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LOWER SILURIAN BRYOZOA.

HK. O, ULRICH.

[EXTRACTED FROM VOL. III OF THE FINAL REPORT OF THE GEOLOGICAL AND
NatuRAL History SURVEY OF MINNESOTA. |

 
CHAPTER IV.

ON LOWER SILURIAN BRYOZOA OF
MINNESOTA.

BY E. O. ULRICH.

INTRODUCTORY REMARKS.

To the Bryozoa must be accorded the first rank among the various classes of
fossils that are represented in the Lower Silurian rocks of Minnesota. They are
entitled to this distinction, first, because of the great variety of form and structure
found among them, and, second, because of their exceeding abundance, in the way
of individuals. In both of these respects their representation exceeds that of the
Brachiopoda, which doubtlessly held the second rank, in the approximate ratio of two
to one. So plentiful are their remains in some of the beds, particularly in the shaly
members, that they may be said to constitute no inconsiderable part of the strata.
In the Trenton shales the intercalated plates of limestone are literally covered with
them, and they are not rare even in the massive limestones above and beneath the
shales, which were deposited under conditions much less favorable to their develop-
ment. In short, of every impartial collection of the Lower Silurian fossils ot Minne-
sota, the Bryozoa necessarily constitute a large portion, not only of the number of
species and specimens, but of its bulk as well.

The importance of the Bryozoa from the view of the stratigraphical geologist,
is again second to no other class of fossil remains. Many of them have a wide geo-
graphical distribution, and as they usually occur in greater or less abundance, and
are very persistent in their characters, their value as data upon which to base cor-
relations of strata at widely separated localities cannot be overestimated. Many of
them, especially of the suborder Trepostomata, are serviceable even where other fossils
are too imperfect, since with the aid of thin sections mere fragments can often be

identified with certainty.
[96]
BRYOZOA. 97

Introduction.]

Living Bryozoa are all inhabitants of water, and mainly of the sea, occurring in
all zones and at varying depths, though seeming in general to prefer clear and shal-
low water. With the single exception of the genus Loxosoma, they are composite
animals, which by the combined efforts of the individual polypides built up colonies
of greater or léss extent, and of either a calcareous, corneous, or membranaceous
composition, by means of repeated, continuous gemmation. These colonies, in both
the living and fossil forms, present so great a variety of form and habit, that it is
difficult if not impossible, to express their growth by any definite formula. Some-
times they grow in plant-like tufts, composed of series of cells variously linked
together ; sometimes they spread over shells and other foreign bodies, forming en-
tire crusts of exquisite pattern, or delicately interwoven threads ; sometimes they
rose into coral-like masses, branching stems, and narrow or broad fronds; at other
times the cell-bearing branches formed most beautiful and regular open-meshed
lacework. | |

However diverse the external aspect of the combined product, the small builders
themselves conform to a simple and quite definite type. Considered briefly, the
polypide consists of an alimentary canal in which three distinct regions, an cesopha-
gus, stomach, and intestine, are recognizable. This is enclosed in a sac, and bent
upon itself so that its two extremities or openings approximate, one of them, the
oral, being furnished with a number of slender, hollow, and ciliated tentacles,
whose movement causes the food to be brought to the mouth. As a rule, the anal
opening is situated without the ring of the tentacles. Generally the upper surface
of the sac is flexible and capable of being invaginated by the action of retractor
muscles attached to the alimentary canal, so that when the animal retreats into its
cell the inverted portion forms a sheath around the tentacles. Heart and vascular
system are wanting, but a nervous ganglion is present, and reproductive organs are
developed in various positions within the cavity of the cell. The ova may be
developed in a special receptacle (marsupium) attached to the zocecium, or in an
inflation of the surface of the zoarium, sometimes called a gonocyst; in other cases a
modified zocecium (gonecium) is set apart for reproductive functions. The general
term oecium is applicable to all these structures. Many Bryozoa are provided with
appendicular organs called avicularia and vibracula. The avicularia may be pedun-
culate, and sway to and fro, or they may be immovably attached to the zocecium.
The vibracula are flexible, bristle-like appendages, set in the excavated summit of a
knob-like elevation or blunt spine. The acanthopores found so frequently among
paleozoic Bryozoa, were probably the supports of similar structures.

=
98 THE PALEONTOLOGY OF MINNESOTA.

EIntroduction.

TERMINOLOGY.

ZOARIUM (=polyzoarium and cenecium auctt.):—The composite structure formed
by repeated gemmation.

Zoccium (=cell auctt.):—The true cell or chamber in which the polypide is
lodged.

Mesopores (interstitial cells auctt.):—The angular or irregular cells which
occupy the spaces between the zocecia in many of the Trepostomata and some of the
Cryptostomata, .

VEsIcuLAR TissuE :—The vesicles which occupy the space between the zoccia
in Pachydictya, the Iistuliporide and other paleozoic Bryozoa.

AcanTHoporss (=spiniform corallites Nicholson, spiniform tubuli Ulrich, Wand-
rohrchen Dybowski) :—The tubular spines which are found in so many paleozoic
Bryozoa, notably Dekayia, Leioclema and Batostoma. :

Mepian Tosvuti (Wandstriinge Dybowski):—Very slender tubes which are present
between the zoccial walls and the median lamine of certain double leaved forms
(e. g. Rhinidictyonide). Their apertures at the surface are slightly elevated and
present the appearance of series of minute granules. The small granules in Rhomb-
opora, Stenopora and other genera, are supposed to be of the same character.

Communication Porzs :—Small peres which pass through the walls of the zowcia
and establish communication between adjacent cells.

Occrum (—evicell, gonocyst, gonecium auctt.):--A modified zocecium set apart for
reproductive functions, the inflation of the zoarium in which the embryos are devel-
oped, or a special receptacle (marsupium) which is attached to the zowecium, and
serves the same purpose.

Diaparacms (—tabule and septa auctt.):--The straight plates which cross the
tubular zocecia and mesopores in the T’repostomata and a few forms of the Crypto-
stomata.

CystipHracms :-—-The convex plates which line the walls of the zocecial tubes in
some of the Trepostomata (Prasopora).

ZO@CIAL COVERS (opercula) and PERFORATED D1APHRAGMS:—Horizontal plates per-
forated subcentrally, covering the zocecia in the Trepostomata. As growth proceeds
in the colony these are left behind in the tubes, and mark the successive stages.

Hemisepta :—-The superior hemiseptum is a plate or laminar projection within
the posterior border of the primitive zocecial aperture, common in the typical Cryp-
tostomata. The inferior hemiseptum is a similar projection on the anterior wall, or
on the median laminz of bifoliate forms, situated a short distance beneath the supe-
rior hemiseptum. One or the other, or both may be absent.
BRYOZOA. 99

Introduction.]

Lunarium :—A more or less thickened portion of the posterior wall in many
paleozoic Bryozoa, which is curved to a shorter radius and usually projects above
the plane of the zocecial aperture. It is of crescentic form, and generally a con-
spicuous feature in tangential sections.

PRIMARY APERTURE :—“ The original orifice” of the zocecium in the Cryptosto-
mata.

SUPERFICIAL APERTURE :—The outer orifice of the tubular prolongation (vestibule)
of the original aperture.

OBVERSE and REVERSE :—Two terms employed to designate, respectively, the
celluliferous and non-celluliferous faces of the zoaria of the Fenestellidw, Acantho-
cladiide, and Phylloporinide.

Dissepiments :--Short non-celluliferous bars connecting the cell bearing branches
in the Fenestellide, at short and regular intervals. The rounded, hexagonal, or quad-
rate meshes of the network thus formed are known as the “ fenestrules.”

 

 

The following brief remarks upon the preservation, methods of study, classifica-
tion, and geological distribution of fossil Bryozoa, the paleozoic forms of America in
particular, may be of assistance to students. A more comprehensive general dis-
cussion of the subject is to be found in the introduction to my recent work in the
eighth volume of the reports of the Geological] Survey of Hlinois.

PRESERVATION.

It is evident that the hard parts of the Bryozoa only could have been preserved
in the fossil state. Equally obvious is the fact that these parts could consist only of
the outer investment of the polypides. The opportunities of the paleontologist are
restricted further to those in which this investment was calcareous, or corneo-calca-
reous. Judging from recent conditions, it would appear that of by far the greater
part of the extinct forms, the colonies or zoaria were capable of preservation, since
in a very large proportion of the living marine Bryozoa the skeleton is calcareous.

Certain changes in the composition and structure of the zoaria have always
accompanied the process of fossilization. Indeed, it is probable that the mineral con-
stituents of all fossils are never the same as they were in the living state. The least,
and I am glad to state, the commonest alteration is where the originally amorphous
calcite has been changed into the crystalline form of that mineral. In most cases
this change has been so gradual, and the crystals formed so minutely, that very little
of the structure has suffered obliteration. Very often many of the minutest details
are still to be recognized. This favorable condition prevails among the majority of
fossil Bryozoa, and is especially remarkable among those derived from Lower Silurian
100 THE PALEONTOLOGY OF MINNESOTA.

[Introduction.

calcareous shales and limestones. When the shales are of a greenish color, as in parts
of the middle third of the Minnesota Trenton shales at Minneapolis, and the shales
of the Cincinnati group at Iron Ridge and Delafield in Wisconsin, the internal struc-
ture was generally completely destroyed through the coarseness of the crystallization.
The same is true in a great measure of forms occurring in dolomitic limestones.

Silicified Bryozoa are comparatively of rare occurrence, especially in Lower and
Upper Silurian rocks. In nearly all cases this method of preservation is confined to
massive limestones, like the Corniferous and St. Louis, and in most cases it is unfa-
vorable, so far as the minute internal structure is concerned. Still, in specimens so
preserved, the external characters are often wonderfully perfect. Such specimens
have been found at the Falls of the Ohio, where they occurred in the decomposed
cherty limestones, from which they were washed free in as perfect a condition, so far
as outer features are concerned, as when they were entombed. Silicified specimens
may also be freed from the rock by means of dilute acids.

A rather common condition of preservation in Devonian and Carboniferous
deposits, is where the calcareous zoaria have been dissolved away, leaving more or
less perfect moulds in the matrix. This is usually a porous chert, like’ that fre-
quently met with in the Corniferous limestone of New York and Canada, and the
St. Louis limestone of Kentucky; or it is an arenaceous shale. This method of
preservation is often very favorable, since, by pressing heated gutta percha into the
empty moulds, it is possible to obtain very serviceable counterparts of the bryozoan
that left them. Such casts, if carefully prepared, often bring out the most minute
details of external marking with surprising fidelity. In the case of such delicate
Bryozoa like the Fenestellide, these moulds are to be preferred to the usual preservation
of calcareous specimens, the latter being too liable to attrition and decomposition.

METHODS OF STUDY.

The bulk of paleozoic Bryozoa, with which the American student is likely to be
chiefly engaged, belong to the Trepostomata and Cryptostomata. In these the inter-
nal structure is of very diverse types, and it is impossible to arrive at a clear concep-
tion of them without the aid‘of thin sections. If possible, these should be prepared
by the student himself, and even if he cannot command one of the new slicing
machines, he may still obtain very excellent results by the simple home-made method
which I am about to describe, and which served me in making thousands of sections.

The materials required are, (1) a piece of sandstone (not too gritty*) eight or ten
inches wide, eighteen or twenty inches long, and of sufficient thickness to insure

 

 

*The Buena Vista freestone of the Ohio Waverly is the best known to me for the purpose,
wes

BRYOZOA. i01

introduction.j

solidity ; (2) a piece of water hone one inch thick, a little wider, and four or five
inches long; (8) a block of wood (walnut is the best) one inch thick, two inches
wide, and four and one-half inches long. The edges of the upper side are rounded to
fit the hand, while in the lower side a shallow excavation, one and one-sixteenth
inches by three and one-eighth, is made to fit the ordinary glass slip. The excava-
tion must be made so that the central portion of the glass slip will bear upon the
block, while the ends may have a little play.

With a strong pair of “wire nippers” a fragment is pinched from the specimen
of which sections are desired. This is taken into the fingers and rubbed upon the
sandstone until the surface is perfectly flat. ‘This is the most important part of the
process, and the greatest care must be exercised to retain (or obtain, as the case may
be) the desired angle. This surface is now rubbed smooth upon the hone, when the
fragment is ready for mounting. A drop of Canada balsam is placed upon the glass
slip, and the ground face of the fragment into it. The slip is now heated (on a
heating stage or over a lamp) and the balsam allowed to boil for five or six seconds,
when the slip is laid upon a horizontal piece of wood to cool. After it is cold the
balsam should be tested, and, if if is not hard and brittle, must be reheated. If of
the proper hardness, the block is moistened, the slip placed into the excavation, and
the superfluous material rubbed away upon the sandstone. When nearly thin
enough it is taken out of the block and finished upon the hone. .

After thoroughly cleaning and drying, the section should be covered with a film
of balsam and a thin sheet of glass. Air bubbles, if any are found, should be expelled
by gently heating the slide and pressing upon the cover glass.

Of course it requires a certain amount of experience and time to make good sec-
tions, yet even the beginner ought to be able to make from twenty to thirty ‘sections
daily, while an expert may increase the number to forty and even fifty.

For reasons about to be mentioned, these sections must be prepared with a

. knowledge of certain peculiarities which are common to the Bryozoa, otherwise the
sections will be misleading. Take for example any ramose or palmate form, and the
student will find that the zoarium of such Bryozoa is composed primarily of two dis-
tinct zones, an inner or axial region where the zocecia are tubular, more or less nearly
vertical, and with very thin walls; and an outer or peripheral region composed of
the same tubes bent outwards at varying angles in order to reach the surface. In
this outer region the zoccia are supposed to have entered the mature condition, and
it is here only that such accessory features as the acanthopores and mesopores are

developed. ‘
102 THE PALEONTOLOGY OF MINNESOTA.

(Introduction.

The necessity of two sections, a vertical and a transverse, is at once obvious, but
as neither of these sections will give us a cross section of the zocecia in their periph-
eral region, where the adult and consequently the most important characters are to
be found, it is evident that a third section must be prepared, which will enable us to
investigate these characters. This section, which is called “tangential,” must divide
the zoarium along a plane parallel with the surface, and only a little below it.

Of bifoliate forms two tangential sections ought to be made, one passing through
the zoarium just below the surface, and the other just above-the median lamina. In
thin examples of this style of growth one large section can be made to show the
characters of the zocecia from their origin to the aperture.

For massive, parasitic, or discoid zoaria, two sections (vertical and transverse)
will ordinarily suffice to bring out the principal characters, but it is advised that
two or more transverse sections be prepared, dividing the zoarium at different hights.

In beginning the study of Bryozoa the first essential is to learn to group them
according to their outer form and mode of growth, The outward form, though
extremely variable when the whole class is taken into consideration, is tolerably
constant for each species, and not infrequently all the species of a genus will adhere
more or less strictly to some particular method of growth. On the other hand many
very distinct types may assume very nearly the same outward form. But the dis-
crimination between these is a second step in the investigation.

The zoaria will usually exhibit one or the other of the following conditions :

1. The parasitic or incrusting zoarium, in which the colony is spread over foreign
bodies. Examples, Ceramoporella, Spatiopora, Stomatopora, Berenicea, etc.

2. The laminar zoarium, is a thin, free expansion, having the lower side covered
by a wrinkled epitheca. Examples, many species of Fistulipora, ete. .

' 8. The massive zoarium, may be of irregular or rounded form, free, attached at
the base, or grow around some foreign body. SEAS species of Monotrypa and
Monticulipora.

4, The discoid zoarium has the form of a plano-convex, or concavo-convex disc;
or it may be conical. The under side is concave or flat and covered with an epi-
thecal crust. Examples, species of Prasopora, Mesotrypa, and Leptotrypa discoidea
Nicholson. |

5. The bifoliate zoarium, in which the zocecia diverge from a double median
lamina or basal plate, and open upon the two surfaces of a foliaceous expansion, or
of flattened branches. Examples, all the Rhinidictyonide and Ptilodictyonidw.

6. The dendroid or ramose zoarium, in which the entire free surface is celluli-
ferous, is very common among paleozoic Bryozoa. Examples, Batostomella, Sue
Hemiphragma, Nematopora.
Introduction.] BRYOZOA. 103

7. The frondescent or palmate zoarium is a modification of the ramose, differing
from it in the flattening and expansion of the branches. Examples are Heterotrypa
Jrondosa d’Orbigny and Homotrypa flabellata Ulrich.

8. The jointed zoarium, in which it is divisible into a greater or less number of
subequal segments. that articulate with each other either terminally or by means of
lateral sockets ; is illustrated in Helopora, Arthroclema and Arthropora.

9. The fenestrated or inosculating zoarium, as in Fenestella and Phylloporina.
The pinnate zoarium is a modification in which the parts of the fronds are feather-
like in their arrangement. Pinnatopora and Acanthocladia are examples.

If the specimens under investigation fall under any except the last two modes
of growth, they will probably exhibit either groups of cell-apertures larger than the
average, commonly raised above the surface and therefore known as “ monticules ”;
or clusters of small cells or smooth spots called “macule.” The monticules may be
rounded, low or conical, and sometimes ridge-like. Examples are shown on plate
XXII, in figs. 1,13 and 24. Frequently there is a combination of large and small cells
as.in figs. 18 and 19 of the same plate. True macule are best developed in the
Fistuliporide, in which. they consist of aggregations of lenticular vesicles, but on
plate XVI, fig. 6, is a good example of the kind in which the cells are tubular. The
non-poriferous margins, so common among the bifoliate Bryozoa, are most probably
a modification of the macule; see plate VIII, fig. 19.

The presence or absence of interstitial cells between the ordinary zocecia, and
the determination of their character when present, is the third step in our investi-
gation. These cells may be of the nature of “mesopores”—small, closely-tabulated
tubes, as in Prasopora and Callopora (plates XVI, XXI, and XXII), or the interspaces
may be occupied by “vesicular tissue” as shown in fig. 4 on plate IX, a vertical
section of Pachydictya frondosa. The zoarium of Monotrypa is characterized by the
complete absence of both mesopores and vesicles (see plate XXVII, figs. 24-29).

Important diagnostic characters are to be observed in the character of the
mouths of the zocecia. They may form short tubular projections (plate I, fig. 6), be
enclosed by a smooth rim or peristome (plate I, figs. 17 and 28), or the rim may be
minutely papillose (plate XIV, fig. 22); or the mouth may be depressed and situated
in a sloping area (plate X, fig. 24). Other conditions, described by the terms “ direct,”
“oblique,” and “confluent,” are obvious without the citation of examples.

Of other external features, the arrangement of the zocecial apertures, and the
character and marking of the interspaces should be noticed.

In the further progress of the investigation, which is now carried on chiefly by
means of thin sections, it is necessary to determine the presence or absence, and the
104 THE PALEONTOLOGY{OF MINNESOTA.

{Introa uction.

character of the “acanthopores,” “median tubuli,” “lunarium,” zoccial covers, and
‘‘hemisepta,” the disposition and character of the “ diaphragms ” and “cystiphragms,”
and the minute structure and independence or amalgamation of adjoining zoccial
walls,

Acanthopores may be small (plate XV, figs. 15 and 17) or large (plate XXIII, fig.
35), and will generally have a very small cavity, but it may be comparatively large
as in Batostoma (plate XXVII, fig. 10). :

Median tubuli may be present between the mesial lamin of bifoliate forms and
between the erect portions of the zoccia (plate IX, figs. 5 and 12).

The lunarium is shown in several types on plate 28. Zocecial covers usually
have a small subcentral perforation ; they may be smooth (plate XXU, fig. 23) or
with a radial ornamentation (plate XXIII, fig. 26). The opening may be laterally
situated, and is often closed.

Hemisepta occur chiefly among the Cryptostomata. On plate VI, figs. 7a and 8
represent good examples of the superior one, while fig. 20 on plate XIV, shows the
appearance of the inferior hemisepta. :

Diaphragms may be remote or crowded (plate XXII, figs. 9, and 38), present in
the axial region (see vertical sections on plate XXIII) or absent (plate XXVI, figs. ] and

29). As arule they are complete and straight, but they may be incomplete as in
Hemiphragma (plate XXIV); and they are always more abundant in the mesopores
than in the true zocecial tubes. Cystiphragms when present, occur in conjunction
with the diaphragms. Usually they overlap each other, as in most of the vertical
sections on plate XVI. Occasionally they are separated and appear as semicircular
lines lining one or both walls of the zocecial tubes in vertical sections, as in fig. 16
of the same plate, In other cases they are oblique or funnel-shaped, as in figs, 3, 4,

and 5, on plate XVII,

. In most Bryozoa the walls of contiguous zocecia are strictly independent and sep-
- arable from each other, but in the Ceramoporide and Fistuliporide, they are com-
pletely fused together.

Among the remaining characters that are brought out by thin sections, it is
important to observe the relative length and shape of the primitive or axial portion
of the zocecial. tubes, and the strength and character of the curve in which they
approach the surface.

CLASSIFICATION.

The class Bryozoa is divided by Ray Lankaster into two very unequal subclasses,
the Holobranchia, in which the lophophore, or ring of tentacles, is unbroken and con-
tinuous, and the Pterobranchia, in which it is divided into two plumed arms or pro-
cesses, bearing a resemblance to the branchial appendages of the Brachiopoda.
BRYOZOA. 105

Olassification.]

According to Nitsche the Holobranchia are again divisible into two very unequal
groups, the Ectoprocta, in which the lophophore surrounds the mouth only, and the
Entoprocta, in which it encloses both the orifices of the alimentary canal. |

The former division embraces the great majority of the Bryozoa, and the second
of the two orders, Phylactolemata and Gymnolemata, of Allman, into which it is
almost universally divided, comprises, with very few exceptions, all the living and
fossil marine forms; In the Phylactolemata the lophophere is open on one side and
horseshoe-shaped ; in the Gymnolemata it is complete and circular.

The second of these orders has been divided into five suborders, the Chilostomata,

Jry ptostomata, Trepostomata, Cyclostomata, and Ctenostomata, all of which seem to be
represented in the paleozoic rocks of America.

=

SYSTEMATIC CLASSIFICATION OF PALEOZOIC BRYOZOA.*

Sub-kingdom MOLLUSCOIDEA.

Class BRYOZOA, Ehrenberg.
Sub-class HOLOBRANCHIA, Ray Lankester.
Order GYMNOLEMATA, Allman.
Sub-order CHILOSTOMATA, Busk.

Orifice of zocecium situated laterally, of smaller diameter than the zocécium,
closed by a movable cover (operculum). Ova usually matured in external marsupia.
Appendicular organs (avicularia and vibracula) frequently present.

Family PALESCHARIDZ, Ulrich.

Genus: Paleschara HALu.

Family WoRTHENOPORIDA, Ulrich. (Provisional)

Genus: Worthenopora ULRICH.
Family PHACELOPORID®, Ulrich.

Genus: Phacelopora ULRICH.

Suborder CRYPTOSTOMATA, Vine.

Primitive zocecium as in the Chilostomata. Orifice concealed, at the bottom of a
tubular shaft or vestibule, which may become intersected by straight diaphragms or
hemisepta through the direct super-imposition of successively developed layers of
polypides. External orifice rounded, often closed by a perforated or entire cover.
External marsupia and avicularia wanting.

*The classification here published is a slight improvement upon the scheme in vol. viii, Il. Geol.Sur. Rep’ts. That one
represented the state of our knowledge on the subject in 1887-89. 7
106 THE PALEONTOLOGY OF MINNESOTA:

[Classification .

Family PTiLoDICTYONID#, Zittel.

Genera: Ptilodictya LONSDALE, Clathropora HALL, Phenopora HALL, Graptodictya ULRICH, Arthro-
pora U., Teeniodictya U., Ptilotrypa U., StictotrypaU., Stietoporella U., Intrapora HALL, Coscinella HALL.

Family RHINIDICTYONIDA, Ulrich.

Genera: Rhinidictya ULRICH, Eurydictya U., Dicranopora U., Goniotrypa U., Euspilopora U., Phyl-
lodictya U., Pachydictya U., Stictopora HALL. ;

Family CysTopIcryonip#&, Ulrich.

Genera: Cystodictya UnRicu, Coscinium KEYSERLING, Dichotrypa U., Actinotrypa U., Toeniopora.
NICHOLSON, Prismopora HALL, Scalaripora HALL, Evactinopora MEEK and WORTHEN, Glyptopora U.,
Goniocladia ETHRIDGE, Acrogenia HALL.

Family RaINOPoRID#&, Ulrich.
Genus: Rhinopora HA.

Family HELIOTRYPIDZ, Ulrich.
Genus :. Heliotrypa ULRICH.

Family ARTHROSTYLID&, Ulrich.

Genera: Arthrostylus ULRICH, Helopora HALL, Sceptropora ULRICH, Arthroclema BILLINGS, Nema-
topora ULRICH, ? Thamnotrypa HALL.

Family RHABDOMESONTIDZ, Vine.

Genera: Rhabdomeson YOUNG and Youne, Celoconus ULRICH, Rhombopora MEEK, Nemataxis
HALL, Acanthoclema HAuu, Bactropora HALL, ? Tropidopora HAuu.

Family STREBLOTRYPID&, Ulrich. .
Genera: Streblotrypa ULRICH, Cyclopora Prout, ? Proutella ULRICH, ?Cycloporeila U.
Family SPHRAGIOPORID&, Ulrich,
“Genus: Sphragiopora ULRICH.
Family FRENESTELLIDA, King.

Genera: Fenestella LONSDALE, Semicoscinium Prout, Fenestrapora HALL, Isotrypa HALL, Tectuli-
pora HALL, Unitrypa HALL, Hemitrypa PHILLIPS, Helicopora CLAYPOLE, Archimedes LESUEUR, Lyropora
HALL, Fenestralia Prout, Polypora McCoy, Thamniscus Kine, Phyllopora Kine, Ptiloporina HALL,
Ptiloporella HALL, ? Loculipora HALL.

= Family ACANTHOCLADIIDA, Zittel.

Genera: Pinnatopora VINE, Septopora Prout, Acanthocladia Kine, Synocladia Kine, Diplopora
Youne and YounG, Ptilopora McCoy, ? Icthyorachis McCoy, ? Penniretepora d’ORBIGNY, ? Ramipora

TOULA.
Family PHYLLOPORINID#, Ulrich.

Genera: Phylloporina ULRICH, Chainodictyon Forrste, Drymotrypa ULRICH, ? Crasaula HALL.
Suborder TREPOSTOMATA, Ulrich.

Zocecia superimposed directly one upon the other so as to form long tubes
intersected by straight or curved partitions (diaphragms and cystiphragms), repre-
senting the covers and floors of the successive layers. Two regions are distinguish-
able in the tubes, an axial or “immature” region in which the diaphragms are
remote and the walls thin and prismatic; and a peripheral or “mature ” region in
which the walls are thickened and otherwise changed, the transverse partitions
more abundant, and accessory elements, such as mesopores and acanthopores, devel-
oped. Zocecial covers with a small central orifice.

Family Monvricuiroripa«, Nicholson.

Genera: Monticulipora d’ORBIGNY, Atactoporella ULRICH, Homotrypella ULRICH, Peronopora NicH-
OLSON, Homotrypa U., Prasopora NICHOLSON and ETHRIDGE, Mesotrypa U.
BRYOZOA. 107

Classification. ]

Family HETEROTRYPID#, Ulrich.
Genera: Heterotrypa NicHOLson, Dekayia EDWARDS and HaimeE, Petigopora U., Dekayella U.
Family CALLOPORIDA, Ulrich.
Genera: Callopora HAUL, Calloporella U., ? Aspidopora U.
Family TREMATOPORIDZ, Ulrich.
Genera: Zrematopora HALL, Nicholsouella U., Constellaria DANA, Stellipora HALL, Idiotrypa U.
Family BATOSTOMELLID®, Ulrich.

Genera: Batostomella U., Stenopora LONSDALE, Anisotrypa U., Bythopora MILLER and DYER, Cal-
loirypa HALL, Leioclema U. .
Family AMPLEXOPORID2, Ulrich.

4

Genera: Amplexopora U., Monotrypella U., Petalotrypa U., Atactopora U., Leptotrypa U., ? Disco-
trypa U.

Family DIPLOTRYPID2, Ulrich.
Genera: Diplotrypa NICHOLSON, Monotrypa NICHOLSON, Batostoma U., ? Hemiphragma U. 7
Family CERAMOPORIDZ, Ulrich.’

Genera: Oeramopora HALL, Ceramoporella U., Crepipora U., Diamesopora HALL, Chiloporella U.,
Ceramophylla U., Anolotichia U., Spatiopora U.

Family FIstuLivorip 2, Ulrich. »

Genera: Fistulipora McCoy, Eridopora U., Chilotrypa U., Meekopora U., Strotopora U., Lichenotrypa
U., Buskopora U., Selenopora HALL, Pinacotrypa U.

Family BoTrRYLLOPoRIDA, Miller.
Genus: Botryllopora NICHOLSON.

Suborder CYCLOSTOMATA, Busk.

Zocecia very simple, tubular, with a plain, inoperculate, circular orifice ; wall
thin, minutely porous. Marsupia and appendicular organs wanting.

Family TUBULIPORID&, Busk.

Genera: Stomatopora BRONN, Proboscina AUDOUIN, Berenicea LAMOUROUX, Diastoporina U.,
9 Hedrella HALL, ? Hernodia HALL, ? Reptaria ROLLE.

Family FRONDIPORID®, Reuss.
Genus: Scenellopora ULRICH. \
Family ENTALOPHORIDA, Reuss.
Genera: Clonopora HALL, Mitoclema U:, Diploclema U., Protocrisina U., ? Cystopora HAL...

Suborder CTENOSTOMATA, Busk.

Zocecia usually isolated and developed by budding from the internodes of a distinct
tubular stolon or stem. Orifice terminal, closed by an operculum of set. Zoarium
horny or membranaceous. Marsupia wanting.

*

Family ASCODICTYONID-£, Ulrich.
Genera: .iscodictyon NICHOLSON and ETHRIDGE, Rhopalonaria U., Vinella U.
108 THE PALEONTOLOGY OF MINNESOTA. ee saa
[Distribution .

GEOLOGICAL DISTRIBUTION.

It is a singular fact that no remains whatever of Bryozoa are known from rocks
of earlier date than the Chazy limestone of the Lower Silurian System. Here the
class suddenly leaps into a prominence, not only in the way of individual represen-
tation, but in the matter of diversity of structure, that is both surprising and difficult
of explanation. Nor was it, as might be expected, the simpler types that prevailed
here. On the contrary, it is the more complex types like the Trepostomata and Cryp-
tostomata that are the most abundant and diverse in their development. What may
be even more surprising is that every suborder known in the fossil state was repre-
sented before the close of the Lower Silurian era.

The vertical range of a few of the Lower Silurian genera (Stomatpora and Beren-
icea), is likewise remarkable, and not equalled, so far as known, in any other class of
animals, excepting the Brachiopoda, of which the genus Lingula, the same as the
bryozoan genera alluded to, has living representatives. Still, as a rule, the vertical
range of Bryozoa is restricted to comparatively narrow limits, and most genera and
many families fail to pass from one system of rocks to the next.

Lower Sinurian System: As has been stated, true Bryozoa are first met with
in the Chazy rocks of this system. In this group, excepting some of the calcareous
strata in New York and Canada, originally referred here; the conditions were often
quite unfavorable, not only for their preservation but for their development as well.
In the excepted beds several species of Phylloporina and Rhinidictya belonging to
the Cryptostomata, a considerable number of mostly undetermined Trepostomata, and
Mitoclema, a genus of the Cyclostomata, have been found. Following the rocks west-
ward from Canada the calcareous beds are lost, but the arenaceous portion, there
known as the St. Peter sandstone, a formation totally unfitted for their preserva-
tion, increases in thickness, and in Minnesota seems to be the only representative of
the formation. The marble beds at Knoxville, Tennessee, which probably belong to
the Chazy, are full of the remains of T’repostomata, none of which have, as far as we
know, yet received critical study.

Following the Chazy are the Birdseye and Black River limestones and shales.
The first of these divisions has a wide geographical distribution, being known from
New York and Canada to Tennessee and Kentucky, as a fine-grained, massive or in
parts somewhat shaly limestone. The shaly layers are full of Bryozoa, among
which the Cryptostomata are preeminently developed. In Minnesota the greater part
of the “Trenton limestone” and the lower two-thirds of the shales resting on it, are
probably equivalent strata. Here the limestone is comparatively barren of Bryozoa,
but the shales, on the contrary, are exceedingly rich, affording also a greater diversity
Distribution ] BRYOZOA. 109

of structure than is known from any of the more southern and eastern localities for
- the group. :

Among the Cryptostomata, hoth the Ptilodictyonide and Rhinidictyonidw reach
their maximum development in this group, while the Arthrostylide and Phylloporin-
ide are both well represented. The Trepostomata likewise are strongly represented,
and in the Minnesota shales of the group every family of the suborder has been rec-
ognized. The Cyclostomata come in with Stomatopora proutana, a species that is con-
tinuously present to the top of the Lower Silurian, and Berenicea.

In the Trenton limestones and shales proper, the Cryptostomata have lost some
of their strength, whilst that of the Tvrepostomata is increased by the addition of
several genera——Prasopora, Monticulipora, Stellipora and Diamesopora. The Cyclo-
stomata add Protocrisina, Diploclema, Scenellopora, and Diastoporina.

Nearly all the genera now introduced continue to the top of the Lower Silurian,
and before the close of the era we find a representative of the last of the five sub-
orders, the Chilostomata, in a species of Paleschara. The Trepostomata, however,
again add greatly to their numbers in the Cincinnati group, in which nearly 200
distinguishable forms of this suborder are known to me. These belong to 35 genera,
giving every family, with the exception of the Fistuliporide, a strong representation.
Of the Cyclostomata also the indivividuals and species became more numerous, while
the Ctenostomata added another species of Vinella and the new genus Rhopalonaria.

Upper Siturian System: The Bryozoa in the rocks of this system are very
different from those of the Lower Silurian. The Trepostomata are greatly reduced
by the almost total extinction of the families Monticuliporide and Heterotrypide, and
a considerable reduction in the Calloporide, Amplexoporide, Diplotrypide, and the
Ceramoporide. But the Fistuliporide, a family that reached its greatest development
in Devonian and Subcarboniferous times, became prominent here. Of the Cyclosto-
mata we have only Diploclema sparsum, a Niagara fossil, of the Ctenostomata, a few
species, and of the Chilostomata, likewise only a few forms of Paleschara. But the
Cryptostomata inaugurate a new and vigorous start. Two new genera, Clathropora
and Stictotrypa, are added to the Ptilodictyonide, while the genera Ptilodictya, and
Phenopora, of the same family, became fully established. Rhinidictya, Pachydictya
Phylloporina, Drymotrypa, Helopora and Nematopora, belonging to three other families
of the suborder, are also well represented. The Fenestellide, of which but a single
Lower Silurian species is known, increase in abundance and variety from the Clinton
to the Lower Helderberg, in which most of the generic types of the family, some of
them, however, not yet fully established, are already distinguishable. Numerous
species of Fenestella and Polypora, and one or more each of Unitrypa, Hemitrypa,
110 THE PALEONTOLOGY OF MINNESOTA.

[Distribution.

Isotrypa, Tectulipora, Semicoscinium, Ptiloporina, and Helicopora, have been described.
The Acanthocladiide begin in the Lower Helderberg with a few species of Pinnatopora
and Icthyorachis, and Rhombopora, belonging to another family of the suborder, has
one species in the Niagara and several in the Lower Helderberg. The Cystodictyon-

ide, essentially a Devonian and Carboniferous family, is also met with for the first
time, a species of Dichotrypa having been described from the Niagara of Illinois, and
one or two of Cystodictya from the Lower Helderberg of New York. Rhinopora is
known only from the Clinton.

The absence of so many characteristic Lower Silurian types, and the presence
of most of the genera that are strongly developed in the Devonian, proves, so far as
the Bryozoa are concerned, that the break between the Lower and Upper Silurian is
sharper than the one between the Upper Silurian and the Devonian.

Devonian System: Several hundred species of Bryozoa have been described
from the rocks of this age. The great mass of these are Cryptostomata, and of these
the majority belong to the Fenestellidw. Every genus of this family, excepting
Fenestralia, Lyropora and Archimedes, is more or less largely represented. To the
same suborder belong Cystodictya, Dichtyotrypa, Prismopora, Scalaripora, Coscinium
Teniopora, Glyptopora, and Acrogenia, of, the Cystodictyonidw; a Corniferous species of
Ptilodictya (the last known of the genus), T'eniodictya, Intrapora, and Coscinella, of
the Ptilodictyonidw ; Euspillopora, of the Rhinidictyonidw ; Rhomboporu, Nemataxis, Acan-
thoclema, and Bactropora, of the Rhabdomesontide; Streblotrypa; and Pinnatopora and
Ptilopora of the Acanthocladiide. The Cyclostomata are included in the genera Clono-
pora, Cystopora, Hederella, Hernodia, and Reptaria; Ascodictyon represents the Cteno-
stomata. The Trepostomata are represented chiefly by numerous species of Fistulipora
and one or more of Hridopora, Chilotrypa, Meekopora, Strotopora, Lichenotrypa, Busk-
opora, Selenopora, Pinnacotrypa, Botryllopora, Monotrypella, Amplexopora, Petalotrypa
Batostomella, Leioclema, and Dekayia,

SUB-CARBONIFEROUS System: The Bryozoa of this age are very similar to those
of the Devonian, and the majority of the genera of either are common to both sys-
tems. The principal difference is found in the absence of some of the peculiarly
modified Devonian types of the Fenestellidv, like Unitrypa, Loculipora, Fenestropora, etc.
They are, however, replaced by the equally interesting genera Archimedes, Lyropora
and Fenestralia. Among the Cystodictyonidw we miss Scalaripora and Acrogenia, but
their vacant places are more than filled by the remarkable genera E'vactinopora and Ac-
tinotrypa. Other Cryptostomata are Teniodictya, ? Stictoporella, Pinnatopora, Septopora,
Ptilopora, Diplopora, Sphragiopora, Coeloconus, Rhombopora, Bactropora, Acanthoclema,
Streblotrypa,{Cyclopora, Proutella and Heliotrypa. The three last named, together
Distribution.] BRYOZOA. 111

with Worthenopora, belonging to the Chilostomata, are new types. Among the T'repo-
stomata, the Fistuliporide are abundant, and Stenopora, Leioclema, Anisotrypa, and
Batostomella not uncommon. Both the Cyclostomata and Ctenostomata are poorly
‘represented, each by one or two insignificant species.

CARBONIFEROUS System: The rocks of this age are mostly unfavorable for the
preservation of the Bryozoa, and only a few localities are known in this country
where good specimens may be obtained. With the exception of Stenopora and Fistu-
lipora all the observed forms belong to the ecryptostomatous genera Fenestella,
Polypora, Thamniscus, Acanthocladia, Pinnatopora, Septopora, Diplopora, Sphragiopora,
Chainodictyon, Prismopora, Cystodictya, and Rhombopora.

In America Bryozoa are rare or entirely unknown in the strata above the paleo-
zoic. ost of the species known are from the Cretaceous and Tertiary rocks of New
Jersey, Mississippi and Arkansas. In Europe the Triassic system is equally poor in
Bryozoa, but in the Jurassic they are represented by nearly eighty species, most of
them Cyclostomata. This suborder continues to be almost exclusively represented to
the Cenomanian in which the Chilostomata are present, though not yet in very great
numbers. Even in the Upper Cretaceous, from which d’Orbigny mentions 662 species,
the Cyclostomata and Trepostomata are nearly twice as numerous as the Chilostomata.
In the Tertiary rocks the Cyclostomata have become less numerous and the Chil-
ostomata more abundant, the ratio of representation at the close of the age being
approximately like the present.
112 THE PALEONTOLOGY OF MINNESOTA.
[Vinella

Class BRYOZOA, Ehrenberg.
Order GYMNOLAIMATA, Allmann.

Sub-ordery CTENOSTOMATA, Busk.
Family ASCODICTYONIDA, Ulrich.

Genus VINELLA, Ulrich.

Vinella, ULRICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 173.

Zoarium attached to foreign bodies (shells, etc.), consisting of exceedingly
slender, ramifying, thread-like, tubular stolons, arranged more or less distinctly in
a radial manner. Surface of tubes sometimes faintly lined longitudinally. A row
of widely separated small pores along the center of the surface of the tubes. Zocecia
unknown.

Type: Vinella repens Ulrich.

The fossils for whose reception this genus was proposed are regarded as related
to Vesicularia, Thompson, and probably also to Mimosella, Hincks, both of them
genera of recent Bryozoa. The zocecia must have been deciduous and developed by
budding from the creeping stolons at the points now represented by the small pores.
The form that is designated the type of the genus, though one of the rare fossils of
the Trenton shales of Minnesota, is justly entitled to that distinction, because it is,
so far as our knowledge at present extends, the earliest existence of the genus.
Similar organisms are known to occur more or less rarely in the Hudson River,
Niagara, ? Hamilton and Chester groups of rocks in America, while in the Wenlock
of England and Gotland, the Ascodictyon radiciformis Vine, is unquestionably a con-
generic form. Still another form that I would refer to this sub-order is repre-
sented in my collection by several zoaria from the Upper Coal Measures at Spring-
field, Illinois.

In the absence of the zocecia a satisfactory classification of these mostly obscure
organisms is perhaps impossible. Our observations are limited to the creeping sto-
lons which, even in the recent Ctenostomata, are but illy diagnostic of generic types.
Better material, carefully studied, may later on demonstrate the advisability of
erecting other genera for some of the types now classed as Ascodictyon and Vinella.
In the present state of our knowledge it is also most difficult to decide the exact
limits of the genus Ascodictyon, Nicholson and Ethridge, jun., and the only plan that
now appears feasible is to include all, and only such forms as possess the ovate or
118
Vinella, Ascodictyon.] BRYOZOA.

pyriform vesicles. As Vinella, on the other hand, I would class those forms in which
they are absent. According to this arrangement the Ascodictyon radiciformis Vine,
would fall under Vinella. Not eo, however, the A. jiliforme of the same author.
This species, so far as I can learn, even in its most simple form, has always an occa-
sional “lagena-like vesicle developed on the sides of the thread,” while some of its
more complex varieties make a decided approach toward the Devonian type of the
genus, A. stellatum Nicholson and Ethridge, jun.

In the accompanying cut (fig. 8), a represents a cluster of vesicles of Ascodictyon
stellatum, with a portion of the delicate stolon that connected it with similar clusters.
One example in my collection consists of eight of such clusters. In the majority of
the specimens seen, however, the clusters are much less regular, and in many cases
the vesicles are distributed with little or no regularity over,the surface of the body
to which the zoarium is attached. In all cases, when the fossil is in a good state of
preservation, these vesicles, whether isolated or arranged in radial aggregations
will be found to be connected with each other by a delicate filament; and in this

species at least, the surface of the vesicles exhibits a large number of minute pores.
Fie. 8.

 

Figure } of the same cut represents a natural size view of the only specimen seen
of the Cincinnati form, that I propose naming VineLLa rapratis. It consists of four
principal colonies or nuclei, growing upon an Orthoceras. Only the form is preserved,
and even that not well. However, sufficient remains to show that it belongs to an
undescribed species, with the probabilities greatly in favor of Vinella as its final
resting place. The radial arrangement is more regular, and the radii straighter
than in any other form of the genus known to me.

Figures c and d of the same cut illustrate an unquestionable species of Vinella,
of which a number of excellent specimens were collected in the Niagara shales near
| Waldron, Indiana. One of the figures is magnified four and a half diameters, the

—8
114 THE PALEONTOLOGY OF MINNESOTA
[Rhopalonaria, Vinella.

other eighteen. In the absence of good examples of the English Wenlock species,
Vinella radiciformis Vine, sp., which these specimens must greatly resemble, I propose
to designate the American form provisionally as var. CONFERTA, in allusion to the
unusually close development of the nuclei.

The inclusion of all the paleozoic Ctenostomata.in one family, the Ascodictyonide,
(see Geol. Sur. Ill., vol. viii, p. 835) is likewise only a provisional arrangement.
Indeed, I am satisfied that Rhopalonaria, Ulrich, at least, which is evidently related
‘to the recent Arachnidium, Hincks, belongs to a distinct family.

Figure 8e is taken from the best example of Rhopalonaria venosa Ulrich, now at
hand.* This species, so far as known, is restricted to the upper beds of the Hudson
River group, and the specimen now illustrated is from those beds at Waynesville,
Ohio. Usually nothing remains to attest the former presence of this bryozoan,
except a series of shallow excavations in the substance of the body upon which it
grew. These excavations, however, correspond very well with the form, or rather,
the outline of the cells and extremely delicate connecting stolons of the zoarium it-
self. The latter must have been quite liable to destruction during the process
of fossilization, and, though diligently searched for, not a single example, so far as I
am aware, has yet been found in which it is preserved in even a fairly satisfactory
manner. In the best specimens the stolons are clear enough, but the swollen por-
tion of the zowcia is always more or less obscure. Now and then, it is true, some
evidence is presented to show that the orifice was situated near one end in the center
of a slightly elevated portion of the surface. These facts, though unfortunate, tend
nevertheless to establish the ctenostomatous affinities of the fossil. If, as already
intimated, Rhopalonaria is related to Arachnidium, then perfect zoarial preservation
is not to be expected. On the contrary, if such a condition were common, as in cal-
careous zoaria, the relationship might well be doubted, since the almost membran-
aceous zoarium of Arachnidium and many other Ctenostomata, is, perhaps, quite
incapable of preservation in a fossilized state.

VINELLA REPENS Ulrich.

PLATE I, FIGS. 1-5,

Vinella repens ULRICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 174.

Original description.—“Zoarium repent, the stolons delicate, thread-like, often
longitudinally striate, straight or flexuous; from 0.06 to 0.11 mm. ‘in diameter ;
bifurcating often and sometimes arranged in a radial manner about a central node.
- Where best. preserved, very small pores arranged uniserially along the center of the

*The original type of the genus and species has been mislaid or lost.

 
BRYOZOA. 115

Stomatopora.]

upper surface of the threads; about eleven in 2.5 mm. Zocecia unknown, probably
deciduous.”

In the Hudson River species, V. radialis, the average thickness of the stolons is
a little less. They are also straighter and arranged quite regularly in a radial man-
ner. In the Niagara form, V. radiciformis, var. conferta, the Soploms are likewise more
slender and the nuclei much more frequent.

Formation and locality—Rare in the upper third of the Trenton shales at St. Paul, Minnesota. All
the specimens seen have grown upon valves of Strophomena septata Winchell and Schuchert.

Sub-order CY CLOSTOMATA, Busk.

Genus STOMATOPORA, Bronn.

Alecto, LAmx., 1821, BLAINVILLE, JOHNSTON, M. Epwarps, Busk, etc. (Not Alecto, Leach, 1814.)

Stomatopora, BRonN, 1825, Pflanzenth., p. 27. D’ORBIGNY, 1852, Pal. Franc. t. v, p. 883. HAImE,
1854, Bry. Foss. Form. Jurassic, p. 159. ULRICH, 1882, Jour. Cin.
Soc. Nat. Hist., vol. v, p. 149, and 1890, Geol. Sur. Ill., vol. viii,
p. 367. MILLER, 1889, N. Amer. Geol. and Pal., p. 825.

Stomatopora (part.), HINCKS, 1880, Brit. Mar. Polyz., p. 424.

Aulopora (part.), GoLDFuss, Reuss, HALL, NICHOLSON.

Zoaria adnate ; zozcia subtubular, club-shaped, or ovate, not immersed, arranged
in single branching series; apertures subterminal, more or less elevated, circular ;
walls finely porous.

Type: Alecto dichotoma Lamouroux.

In drawing up this diagnosis I continue to follow Jules Haime and d’Orbigny in
discriminating between the uniserial and multiserial forms, despite the fact that a
_tendency to unite them under one name has of late become manifest. Hincks, for
instance, places species here having precisely the same zoarial habits as the Probo-
scina frondosa (pl. |, fig. 28) of the Hudson River rocks. He would probably go far
enough in this direction to include even Berenicea minnesotensis., And yet he retains
Diastopora, with Berenicea as asynonym. The resulting classification is, to my mind,
anything but satisfactory. With me the greatest difficulty is, not to separate the
uniserial forms, but to draw a line between Berenicea (as typified by B. diluviana
Lamouroux) and the bi- and: multiserial forms of which Proboscina auloporoidea
Nicholson, sp., P. tumulosa, P.frondosa Nicholson, sp., and Berenicea minnesotensis are
progressive examples. That some of these, and several Secondary, Tertiary and re-
cent species of this type, sometimes have the zocecia arranged uniserially at the base
and at the beginning of the branches is scarcely a sufficient reason for regarding them
as congeneric with such invariably uniserial forms as Stomatopora dichotoma Lamou-

roux, 8. proutana 8. A. Miller, S. inflata Hall, sp.,anda host of others. As I view the
116 THE PALEONTOLOGY OF MINNESOTA.
‘ {Stomatopora.

matter, the former in their mature or ultimate development, are much nearer Berenicea
(Lamouroux, Haime, Zittel and others ; Diastopora of Busk and other British authors).
Sharply defined genera are an impossibility in nature. She follows paths altogether
too intricate to be expressed in a system of classification. The best result that we
can obtain must be a happy medium between convenience and natural affinity. Con-
venience, and stability as well, are surely sacrificed when we throw together a number
of genera and then divide the composite genus, that has now been made to assume
the rank of very nearly a family, into sections of questionable utility that no one is
obliged to recognize, because they have no established ‘validity in any system of
classification. Is it not better, because it is convenient and saves time, to have it
understood at once that when one says Stomatopora, he refers to uniserial forms ;
Proboscina, to forms with similar zocecia but partly immersed and in two or more
series, and Berenicea, to such as have them forming entire, flabellate, circular or
irregular crusts ?

The only change from the arrangement here retained that I am willing to enter
into, and for which good and probably sufficient reasons can be advanced, is one
that would drop Proboscina, leaving Stomatopora to stand as at. present for the
uniserial species, and extend Berenicea so as to include the ground now occupied
by Proboscina. ;

SromaTopora TENUISSIMA Ulrich.
PLATE I, FIGS. 6and 7.

Stomatopora tenuissima ULRicnH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 175.

Original description“ Zoarium adnate, consisting of frequently branching
uniserially arranged zocecia. Zocecia exceedingly slender, about seven in 8-mm.,
each from 1.0 to 1.5 mm. long, usually increasing very gradually from the proximal
end, where the diameter is about 0.04 mm., to near the slightly bulbous anterior or
‘upper end, which varies from 0.11 to 0.18 mm. in diameter. Aperture circular, small,
about 0.05 mm. in diameter, situated very near the anterior end of the zocecium.

“This and S. turgida illustrate the extremes of difference in shape and size of
the zocceia of Stomatopora so far noticed. SS. tenuissima is closely related to’ S. prout-
ana Miller, but its zocecia are much longer. Miller’s species, with scarcely any
modification, ranges from low in the Trenton (Birdseye limestone) to the top of the
Hudson River group.

Formation nad locality.—Toward the top of the Utica horizon of the Hudson River group at Cincin-
nati, Ohio, 150 to 175 feet above low water mark in the Ohio river. :
Rhinidictya, ] BRYOZOA. 117

STOMATOPORA PROUTANA S. A. Miller.
PLATE I, FIGS. 8-12.

Stomatopora proutana 8. A. MILLER, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 39.
Ropalonaria pertenuis ULRICH, 1886. Fourteenth Ann. Rept. Geol. Nat. Hist. Sur. Minn.,, p. 59.

Zoarium adnate, consisting of frequently branching, uniserially arranged zoccia.
Zoecia slender, clavate, about 0.04 mm. in diameter at the proximal end, increasing
gradually in size to from 0.12 to 0.15 mm. at the rounded anterior end ; each 0.6 to
0.8 mm. long, with from eight to tenin 5mm. Aperture subterminal, small, circular,
with a slightly elevated rim-like border ; 0.05 to 0.06 mm. in diameter.

The above describes the usual form of the species, but fig. 12 represents a
variety occurring in the lower layers of the Trenton shales of Minnesota, and in the
“Pierce” limestone of Tennessee, having unusually large zocecia. In this their
length varies from 0.8 to 1.1 mm., while the diameter in the anterior third is gen-
erally over 0.2 mm., and sometimes as much as 0.3 mm.

In ny preliminary report on the Minnesota Bryozoa this species was erroneously
placed under the ctenostomatous genus Rhopalonaria. At the time I thought it
advisable to extend the limits of that genus so as to include these delicate species
of Stomatopora. Later studies have fully demonstrated the fallacy of such a view.

Compared with American species, only S. tenwissima and S. inflata Hall, sp., will be
found to exhibit any close relations. In the first the zocecia are more slender and
longer; in the second they are much more inflated. S. elongata Vine, from the
Wenlock of England, has slightly shorter zocecia of a form very nearly intermediate
between those of 8. ‘prowtana and S. inflata.

Formation and locality.—This species occurs in the ‘‘ Pierce” limestone of Tennessee, the Birdseye
limestone of central Kentucky, and the Trenton shales of Minnesota at Minneapolis, St. Paul and Cannon
Falls; also at Decorah, Iowa. So far it has not been recognized in the Galena, but it is to be found, rather
rarely though, in the Utica horizon at Cincinnati, Ohio, and more abundantly near the tops of the hills at
that locality. It occurs,also higher in the Hudson River rocks at several localities in Ohio and Indiana,
and at Wilmington, Illinois.

Mus. Reg. Nos. 5926, 8066.

StomaTopora InFLATA Hall.

PLATE I, FIGS. 13-21.

Alecto inflata HALL, 1847. Pal. N. Y., vol. i, p. 77.

Hippothoa inflata NICHOLSON, 1875. Pal. Ohio, vol. ii, p. 268.

Stomatopora injlata VINE, Nov., 1881. Quar. Jour. Geol. Soc. London.

Zocecia resembling those of Hippothoa, short and wide when compared with the
preceding species, pyriform, the proximal end contracted and springing from the

under side of the anterior end of the cell beneath ; eight ornine ind mm. Apertures
118 THE PALEONTOLOGY OF MINNESOTA.

[Stomatopora.

circular, direct, with a peristome, about 0.09 mm. in diameter, situated near the ante-
rior end. Mural perforations minute and but rarely preserved.

In the Trenton or typical form of this species the zocecia, as a rule, are less swol-
len and the adnate zoarium divides less frequently than in the better known Cincin-
nati form. In the latter, therefore, the network is closer, and occasionally the
growth is so luxuriant that the rows cross each other to such an extent that but
little space is left between the cells. No distinction, however, can be based upon
these characters since, when good series of specimens are studied, it is found that
among those from Trenton localities some have more than commonly swollen and
crowded cells, while in some of those from the geologically higher localities the
growth is lax and the zocecia comparatively narrow.

Formation and locality.—Trenton group, at Trenton Falls, Néw York; Ottawa, Canada; Cannon
Falls, and other localities in Minnesota where the upper third of the Trenton shales are exposed ; Hudson
River group at Cincinnati, Ohio, (350 to 425 feet above low water mark in the Ohio river), and in the upper
beds at Richmond, Indiana; Wilmington and Savannah, Illinois, and other localities.

Mus. Reg. Nos. 5924, 8045, ’

Sromatopora TurGIDA Ulrich.
PLATE I, FIGS. 22 and 23.

Stomatopora turgida ULRicn, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 176.

Original description —“ Zoarium adnate, consisting of a single branching series of
zocecia. Zocecia comparatively very large, the anterior half much swollen, rapidly
tapering posteriorly, with the slender, tubular proximal end inserted beneath the
turgid anterior end of the preceding zoecium. Five zoecia in 5 mm.; length of
each zocecium varying from 0.85 to 1.30 mm.; the greatest diameter of the anterior
half from 0.4 to 0.6 mm. The longest cells are the least turgid, while the shortest
are the most. Apertures round, bordered by an elevated margin, small, 0.1 mm. in
diameter, and situated about one-fourth of the length of the zceocium from its ante-
rior end.

“T have a number of specimens of this species, and all consist of comparatively
few zocecia. “Nor do the series of cells in any of them branch often ; from which it
appears that: the production of two “gems” was a much less frequent occurrence
than in the related S. inflata Hall. S. turgida is further distinguished from that and
all other species of the genus known to me, by the much larger zocecia.”

Formation and locality.—Upper beds of the Hudsyn River group at Wilmington, Illinois.

x
BRYOZOA. 119

Proboscina.]

Genus PROBOSCINA, Audouin.

Proboscina (part.), AUDOUIN in Savigny, Desc. de l’Egypte, Pol., p. 236, 1826.

Proboscina, d’ORBIGNY, 1852, Pal. Fr. terr. cret., t. v, p. 844. Harms, 1854, Bry, dela form. Jurass.,
p. 10. Ulrich, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 149, and
1890, Geol. Sur. I11., vol. viii, p. 368.

Not Proboscina, of Smrrr and others.

Zoaria wholly adnate. Zoccia as in Stomatopora, excepting that they are more
or less immersed and not uniserial, being arranged in two or more contiguous rows.
For remarks relating to this genus see under Stomatopora.

PROBOSCINA TUMULOSA, 7. Sp.

PLATE I, BIG. 24.

Zoarium adnate, branching dichotomously, or inosculating, in the latter case
forming an irregular large-meshed network. Branches narrow, generally with two
or three, rarely four or five, alternating series of cells. Zocecia subpyriform, or
obovate, not wholly immersed, generally appearing as bulbous swellings on the sur-

“face of the zoarium. Apertures subterminal, contracted, circular, slightly oblique,
about 0.09 mm. in diameter, with a, slight peristome. About five or six cells in
3.0 mm. .
Compared with Proboscina frondosa (plate I, fig. 28) and P. auloporoidea (both
Nicholson, sp.), two Hudson River forms, this species is distinguished by its shorter
-and more bulbous zoccia, their shape being more like those of Stomatopora inflata
and Berenicea minnesotensis. The resemblance to the last is so marked that I would
not be surprised if coming discoveries prove P. tumulosa directly descended from it.

Formation and locality.—Rare in the upper third of the Trenton shales at St. Paul; more abundant
in the same beds near Cannon Falls, Minnesota.

Mus. Reg. Nos. 7620, 8047, 8101.

Proposcina FRONDOSA Nicholson.
PLATE I, FIG. 28.

Alecto frondosa NICHOLSON, 1875. Pal. Ohio, vol. ii, p. 266.
Proboscina frondosa ULRICH, 1889. Contri, to the Micro-Pal. of Canada, pt. ii, p. 28.

A figure, taken from an excellently preserved example of this species, is intro-
duced for the better understanding of, and comparison with, Minnesota Cyclostomata.
This specimen is from the hill quarries at Cincinnati, Ohio, but the species also occurs
in the upper beds of the formation at many localities in Ohio, Kentucky and Indiana,
at Nashville, Tennessee, Wilmington and Savannah in Illinois, and at Stony Moun-
e

120 THE PALEONTOLOGY OF MINNESOTA.

‘ [Berenicea.

tain, Manitoba. My belief that it will yet be found at Spring Valley, Minnesota, and
other points in the southern part of the state, where equivalent beds are exposed, is
therefore within the bounds of probability.

Mus. Reg. No. 8102.

Genus BERENICEA, Lamouroux.

_Berenicea (part.), LAMOUROUX, 1821. Exp. meth. des genres de pol., p. 80.

Rosacilla, F. A. ROEMER, 1840, Verst. des norddeutsch. Kreidegeb., p. 19.

Berenicea, d’ORBIGNY, 1852. Pal. Fr. terr. cret., t. v, p. 858. J. Harmp, 1854, Bry de la form.

Jurass., p.19. ULRicH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p 194,
and 1890, Geol Sur. I1., vol. viii, p. 368.

‘Diastopora, d’ORBIGNY, 1850, and Busk and other English authors. (Not Lamouroux.)

Diastopora, (part.), HINCKs, VINE and others,

Saganella, HALL, 1852. Pal. N. Y., vol. ii, p. 172.

Diastoporella, VINE, 1883. Brit. Assoc. Rep. Foss. Pol., iii; and Proc. Yorks. Geol. Soc., n. s., vol. ix,

pt. ii, p. 190. .

Zoaria incrusting, forming circular or irregular patches. Individual zocecia as
in Stomatopera and Proboscina, but contiguously arranged in more or less regular
‘spreading series,

Type: B. diluviana Lamouroux.

For remarks relating to this genus see under Stomatopora.

BERENICEA MINNESOTENSIS Ulrich.

PLATE I, FIGS. 2, 27 and 29; PLATE II, FIG. 1.

Berenicea minnesotensis ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 58.

Zoarium forming exceedingly thin, irregular crusts upon foreign bodies. The
crust may be entire, with irregularly distributed and unequal non-celluliferous spots,
or, especially at the edges of large expansions, it may throw off broad branches and
include a few open spaces. In one example, provisionally referred here, the latter
are so large and conspicuous that the zoarium may well be described as consisting of
wide, irregularly inosculating branches.* Ordinarily the crust is nearly entire, and
the non-celluliferous spaces, which, like the rest of the surface between the zocecial
apertures, are marked with obscure transverse lines or wrinkles, constitute a con-
spicuous feature. Zocecia more or less immersed, in the latter condition appearing
as subelliptical convex spaces, about 0.2 mm. wide, with an oblique circular aperture,
0.13 mm. in diameter, at their upper ends. In such examples (see fig. 29) the aper-
ture is scarcely produced, but in others, more matured, it is prominent, while all the
remainder of the cell is completely immersed. The arrangement of the zoccia is,

 

*Perhaps this specimen is to be cousidered as indicating a departure that later on resulted in Proboscina tumulosa of this
work.
BRYOZOA. 121

Diastoporina.]

on the whole, inclined to be irregular, though fairly regular longitudinal series, and
sometimes diagonally intersecting rows can generally be made out. The average
number in 2 mm. is five or six,

Compared with B, primitiva Ulrich, from the Hudson River group of Ohio, this
species is distinguished by its larger and less tubular zocecia, the interstitial wrinkles,
and the non-celluliferous spaces. B. vesiculosa Ulrich, from the Utica shales horizon
at Cincinnati, is a nearer relative, but also has smaller zoccia, with the apertures
less prominent. In most respects the position of the Minnesota species is inter-
mediate between the two Ohio species.

Formation and locality—Not uncommon in the lower and middle beds of the Trenton shales, at
Minneapolis and St. Paul, Minnesota.

Mus. Reg. No. 5925.

Genus DIASTOPORINA, Ulrich.

Diastoporina, Ulrich, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 177.

Zoarium bifoliate, in general resembling Diastopora (Lamouroux, not Busk).
Zocecia subtubular, prostrate, immersed ; apertures constricted, subcircular, not
prominent. Interspaces finely punctate and striated longitudinally. ,

As only one species is known, it is difficult, if, indeed, it is not impossible in all
such cases, to determine the really essential characters of the genus. The striation
of the interspaces is a peculiar feature and the chief ground for separating the
species from Diastopora, a genus so far not known in strata older than Jurassic.
The Minnesota species, however, presents many points of agreement with species of
that well known genus, and it may yet be shown that it represents merely an early
type of same. This resemblance or possible relationship is paralleled in Mitoclema,
Ulrich, and Entalophora, Lamouroux ; Diploclema, Ulrich and Bidiastopora, d’Orbigny;
Protocrisina, Ulrich, and Crisina, d’Orbigny; and Scenellpora, Ulrich, and Defrancia,
Bronn, and Discocavea, d’Orbigny. In each case the first is founded upon lower
paleozoic species, while none of the genera with which they compare are as yet
known in rocks earlier than Jurassic. With the exception of Entalophora (?Mito
clema) one or more species of which occur in the Devonian at the Falls of the Ohio,
and in New York (Clonopora, Hall, 1887, Pal. N. Y., vol. vi), none of these cyclostoma-
tous genera are known to have had an existence in Devonian and Carboniferous
times. Precisely the same is true of Stomatopora, Proboscina, and Berenicea.* But

 

* Since writing the above, a paper has been received from the Canadian Geological Survey, in which Prof. J. F. Whit-
eaves describes one species each of Stomatopora and Proboscina, from the Devonian rocks of the far north. At my request,
Prof. Whiteaves kindly sent me the types of the two species. These were carefully examined by me, with the result. that I
stil] hold that we have no positive evidence of the existence of these genera in Devonian deposits. The firstis unquestionably
very closely related to Rhopalonaria botellus Vine, and not a Stomotopora. The other may bea Proboscina, but itisso different
from any type of that genus known to me that I am obliged to view its relations as highly problematical.
122 THE PALEONTOLOGY OF MINNESOTA.
| Distribution.

in these cases the Lower and Upper Silurian species are so nearly like the Secondary,
Tertiary, and recent forms of the genera, that a generic separation has so far seemed
impracticable. And yet, considering their apparent: absence in the Devonian and
Carboniferous deposits, would we not be justified in denying the lineal descent of the
recent forms from the early paleozoic species? However, questions of this kind can™
not be considered as they deserve in the space here at my disposal, and, as they are
also a little out-of place in a publication of this kind, they will be merely touched
upon, leaving their real discussion for some more fitting occasion.

DIASTOPORINA FLABELLATA Ulrich.
PLATE II, FIGS. 2 AND 3.

Diastoporina flabellata ULRIOH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 176.

Zoarium small, arising from an attached basal expansion into thin flabellate
fronds. The largest and only complete example seen is 5.5 mm. wide. Surface
with obscure concentric wrinkles, and fine interrupted striations arranged parallel
with the direction of the zowcia. Under a high power of magnification the latter
appear as delicate lines separating rows of exceedingly minute pores. Zocecia rather
scattering, in young examples partly exposed, appearing as convex oval spaces with
a small oblique aperture, about 0.05 mm. in diameter and but little, if at all, elevated
at the distal extremity. In some fragments of seemingly older examples the entire
cell is immersed, leaving only the aperture, which, in these cases, is nearly direct
and subtubular, to project over the nearly even surface. Their arrangement is often

"quite irregular, particularly in the vicinity of certain small non-celluliferous spots,
but where rows are to be made out, about six or seven apertures occur in 2 mm.
This is the only bifoliate. cyclostomatus bryozoan known to me in paleozoic

rocks.

Formation and locality—Rare in the Galena shales near Cannon Falls and at St, Paul, Minnesota.
At the first locality it is associated with a very interesting fauna, consisting principally of Ostracoda and
minute bryozoans, among the latter species of Nematopora, Helopora and Arthroclema.

Genus MITOCLEMA, Ulrich.

Mitoclema, ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 150; and 1890, Geol. Sur. Ill., vol. viii,
pp. 336 and 369. ;

Comp. Clonopora, HALL, 1886. Pal. N. Y., vol. vi, p. 25; also, abstract Trans. Albany Inst., vol. x:
p. 20, 1881.

Comp. Entalophora, LAMOUROUX, 1821. Exp. meth. des genres de pol., p. 81.

Zoaria ramose, slender, subcircular in cross-section. Zoccia tubular, long, pris-
matic and thin-walled in the axial region, gradually diverging in all directions from
Distribution.] BRYOZOA. 129

an imaginary axis to the surface where they bend outward abruptly, often becoming
free and much produced. Apertures circular, sometimes scattering, usually arranged
in regular transverse or subspiral series.

Type: M. cinctosum Ulrich, Chazy (perhaps lower Birdseye) limestone of Ken-
tucky.

Fuller investigations and comparisons with typical and authentic examples of
Entalophora and Clonopora are necessary before we may be said to be in a position to
decide peimanently the merits of this genus. Entalophora, as now understood by
Hincks and Waters, seems to me to be too comprehensive and might be, with advant-
age to classification, divided into at least two groups of generic rank, and it is not
at all improbable that Mitoclema stands upon unoccupied ground. In the meat@time
no harm can result from the use of the name for these early paleozoic species.

Miroctema(?) munputum Ulrich.
PLATE ITI, FIGS. 4-6.

Mitoclema ? mundulum ULRIcH, 1890. Jour. Cin. Soc. Nat.Hist., vol. xii, p. 177.

Zoarium ramose, very small, the branches cylindrical, 0.5 or 0.6 mm. in diameter,
with faint transverse strie or wrinkles over the spaces between the zocecial apertures.
The latter are drawn out tube-like, about 0.15 mm. in diameter, and project strongly
upward and outward from the surface of the small stems. Their arrangement is in
rapidly ascending spiral series, with four or five in 2mm. As near as can be deter-
mined from the material at hand, the zoccial tubes diverge equally to all sides of
the branches from an imaginary axis.

Owing to the absence of specimens suitable for slicing the internal characters of
this species have not been determined. The generic position is therefore somewhat
questionable, since it may prove to have the structure of Diploclema Ulrich (Geol.
Sur. lll., vol. viii, p. 368), founded upon D. trentonense Ulrich, a similar form occur-
ring in the Trenton limestone of New York. In Diploclema the branches are slightly
compressed, and the zocecial apertures somewhat constricted and less prominent.*

Formation and locality—Associated with the preceding in the topmost beds of the Trenton shales, at
Cannon Falls, Minnesota.

Mus. Reg. No. 8108.

 

*In his paper on Wenlock sbales Bryozoa Mr. Vine has described several similar species which he originally referred to
Spiropora and later to Entalophora- Of these S. regularis is an unquestionable Diploclema and closely allied to our Niagara
D. sparsum Hall, sp. The others I have not had an opportunity of examining.
124 THE PALEONTOLOGY OF MINNESOTA. a
(Rhinidictya.

Suborder CRY PTOSTOMATA, Vine.

Family RHINIDICTYONIDA, n. fam.

Stictoporide, ULRICH, 1890. Geol. Surv. Ill, vol. viii, p. 388.
Stictoporide (part.), ULRICH, 1882. Jour. Cin. Soc. Nat: Hist., vol. v, p. 152.

‘This name is proposed instead of Stictoporide, for the reason that the type genus
is not, as I have heretofore held, properly expressed by the term Stictopora. Since
Hall, the author of that name, and others, insist that 8. elegantula is the type of Stic-
topora, it follows that the genus and family as described by me (Joc. cit.) cannot stand.
In nf Illinois work, namely, I had taken the stand that 9. fenestrata is to be regarded
as the type, and as that species is unquestionably congeneric with Rhinidictya, Ulrich,
(Jour. Cin. Soc. Nat. Hist., vol. v, p. 152), the latter was reduced to synonomy. Though
the minuté internal and external details of structure of S. elegantula have not yet
been made public, enough is known of it to prove conclusively that it represents a

“genus to which S. Fenestrata has no claim. This being the case, Rhinidictya will
stand and include fenestrata.*

Genus “RHINIDICTYA, Ulrich,

Stictopora (part.), HALL, 1847. Pal. N. Y., vol. i, p. 73.

Stictopora, ULRICH, 1890. Geol. Surv. Ill., vol. viii, p. 388.

Rhinidictya, ULRicH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 152; Haw, 1887, Pal. N. Y.,
vol. vi, p. 20. :

“Zoaria composed of narrow, compressed, dichotomously divided branches, with
the margins sharp, straight, and essentially parallel; attached to foreign bodies
by a continuous expanded base. Zocecial apertures subcircular or elliptical, arranged
alternately in longitudinal series between slightly elevated, straight or flexuous ridges,
carrying a crowded row of small blunt spines. Space immediately surrounding aper-
tures sloping up to summits of ridges.” (Geol. Surv. II1., vol. viii, p. 388.)

Type: R. nicholsoni Ulrich, Birdseye Limestone, Kentucky.

This genus finds its strongest development numerically, both as regards species
and individuals, in the rocks of the Trenton formation. The Minnesota shales of
this group are especially rich in specimens, and so far as species are concérned, there
is no other section of the country from which as many are known. Unfortunately,
however, the various forms of the genus are not by any means easily distinguished
from each other. It is true also that of those species which have a wide geographi-
cal range, as for instance from Minnesota to Kentucky and Tennessee, or to New

 

* For objections to the use of Sulcopora, d’Orb., instead of Rhinidictya, see Geol. Surv. Il1., vol. viii, pp. 683 and 687,
125
Rhinidictya.] © BRYOZOA. _

York and Canada, the specimens at each of these localities are marked by individual
peculiarities, causing their identification to be, in some cases at least, unsatisfactory
and generally rather difficult. Nothing less than monographical work can do the
genus justice. Manifestly, even if possible in the present state of our knowledge,
such work would be out of place here.

I shall therefore largely restrict my remarks to the Minnesota forms, while
those occurring in other sections of the country will be mentioned incidentally only,
and chiefly when comparisons are desirable.

RaINIDIOTYA MUTABILIS Ulrich.
‘PLATE VI, FIGS. 1-6, 12-13; PLATE VII, FIGS. 10-23, and 25-28; and PLATE VIII, FIGS. 1-3.

Stictopora mutabilis ( part.) ULRicH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 66.
Stictopora mutabilis, var. minor ULRICH. Ibidem, p.'67. =

Zoarium a branching bifoliate stipe, varying considerably in width and superfi-
cial aspect.

Typical form :—In the commonest or typical form, the branches vary in width
from 2.3 mm. to 3.2 mm., and in thickness from 0.7 mm. to 1.9 mm.; they divide
dichotomously at intervals varying from 7 to 16 mm., but on an average a bifurca-
tion takes place every 10 to 12 mm.; edges generally sharp, but with age become
blunter as the stipes increase in thickness; non-celluliferous margins very scant,
often practically wanting. Zocecia arranged in from ten to eighteen rows ; the usual
number is fourteen or fifteen, but just beneath a bifurcation it generally exceeds
twenty. Between the rows are straight longitudinal ridges, angular and crowned
with a single series of small granules in well preserved young and average examples,
thicker, rounded, and with stronger and more numerous granules in old examples
(see plate VII, fig. 10). In young examples again the spaces between the ends of the
apertures are slightly depressed, causing them (the apertures) to appear as openings
in the bottom of shallow channels. In such specimens (see plate VII, fig. 15) the
interspaces are comparatively thin and the zocecial apertures correspondingly large,
the long diameter of the latter being about 0.20 mm., and the short or transverse

diameter about 0.12 mm. With age the transverse diameter may be reduced to less
_ than 0.5 mm., while the channelled appearance becomes obsolete in the general thick-
ening of the interspaces. In a few fragments, apparently representing the condition
of extreme age, the zocecial apertures are scarcely recognizable, the entire surface
appearing as simply granulo-striate. In most cases the zoccial apertures in one or
more of the marginal rows are directed upward and outward. Measuring trans-
versely, about eleven of the central rows in 2 mm, (extremes ten and twelve); longi-
126
THE PALEONTOLOGY OF MINNESOTA. areas

tudinally, about seventeen zoccia in5 mm. Except in a variety to be considered
presently, the zocecial apertures always appear as direct.

Vertical sections (plate VI, figs. 8 and 5) show that the zocecial tubes, in their
course from the basal (median) plate to the superficial aperture, form an angle of
about 50 degrees with the surface. In the primitive portion of the zoccia (i. e. that
part which lies on each side close to the median laminz) the posterior side curves out-
ward and forward so as to form a curve about equaling one-fourth of a circle. The
anterior extremity of the curve terminates abruptly at the primitive aperture ; from
this point to the surface of the zoarium, or in what has been described as the “ vesti-
bular portion of the zocecium,” the course of the wall is nearly straight. In a few
species of this genus (e. g. R. fidelis and R. minima) the junction between the “ves-
tibule” and the curved posterior side of the “primitive cell”, is prolonged into a
short septum that I have designated as the “superior hemiseptum.” In R. mutabilis,
however, this septum is but little, if at all, developed, the junction being merely an-
guiar. When the section shows the transverse interspaces (this is often the case
because of the great thickness of the interspaces in the vestibular region) they will
be seen to exhibit interrupted dark vertical lines. These. represent the tubular
internal extensions of the minute granulations noticed at the surface. Stages in
the growth of the zoarium may also be determinable. These are marked by dark
lines, sharpest in the inner portions of the zoarium. j

In transverse sections the chief point of interest is the row of minute tubuli
that exists between the two parts of the duplex mesial lamina. (See plate VI, fig. 6.)

Tangential sections present a variety of appearances depending (1) upon the age
of the fragments sectioned, and (2) the depth beneath the surface represented in the
section. Using an old example the section may be made, with judicious manipula-
tion, to show all the conditions through which the zoarium has passed, from the
beginning of the zocecia on the mesial laminz to their mouths. Taking such a sec-
tion, which, to be satisfactory, should not be less than 10 to 15 mm. long, the follow
ing features are likely to result: Starting with the mesial laminz, which will be
recognized as a faintly dark space, the first character worthy of notice are the “median
tubuli.” These are represented by very delicate parallel lines, longitudinal in the
central third of the zoarium, but gradually diverging or curving toward. its edges in
the lateral thirds. Though not yet clearly demonstrated in this species, I neverthe-
less assume it to be a fact (because of observations in other forms possessing such
tubuli) that the “mesial tubuli” connected with the minute tubes between the walls
of the zocecia, the surface extensions of which have been described as granules. (See
plate VI, fig. 18.) Just above the mesial lamine the section presents the basal or
127
Rhinidictya.] BRYOZOA.

priniitive portion of the zoccia as sharply defined, thin-walled, oblong-quadrate
spaces, the end walls of which, while approximately at right angles with the long-
itudinal lines at the center of the zoarium, gradually assume an oblique upward direc-
tion toward the sides. (Compare plate VI, fig. 18.) The next condition is when the
anterior wall or side of the zocecium becomes convex, while the posterior side begins
to extend over the cell till at last the oval aperture is formed. Now the anterior
and posterior walls are no longer recognizable in the section, but the division between
the longitudinal walls is clearly marked by a dark line, that, when the preservation
of the specimen is sufficiently favorable, will be noticed to consist of a connected
series of minute tubuli. Besides these, an occasional dark spot or tubulum may be
noticed in the end spaces. Most of the stages so far described are shown in fig. 13,
on plate VI, and all further phases are to be classed as old conditions. They consist
principally of an increase in the number of minute interstitial tubuli. (See plate
VI, figs. 1 and 4.)

The above description does not include two forms that deserve recognition as
varieties. Their peculiarities are not sufficiently constant to entitle them to the
rank of species. In my preliminary report on the Minnesota Bryozoa (loc. cit.)
another form of the species was separated as var. minor. The better and much
more complete material since studied proves, however, that the specimens so desig-
nated are merely young examples and therefore not deserving of a distinct name.

Var. Mason Ulrich.

The zoarium in this variety is more robust, the branches being wider, in some

cases attaining a width of over 8 mm.; usually the thickness is also greater, but thin
examples are not uncommon. Perhaps the chief peculiarity of the variety is found
in certain grano-striate or smooth spots, which occur at rather irregular intervals
along the center of the branches. The internal structure agrees in all essential
respects with that of the typical form of the species, the only feature not seen in the
latter being the solid macule.

Mus. Reg. No. 5940.

Var. SENILIs, 7. var.
PLATE VI, FIGS. 2 and 3; PLAT#H VII, FIGS. 16 and 17.

In this rather rare form the general appearance of the zoarium is like that of
well developed examples of the typical variety. On comparison, however, it is found
that the non-celluliferous margin is unusually wide and sharply defined. Connected
with this are certain narrow, irregular or subelliptical, depressed spaces just within
the axes of bifurcation. A more important peculiarity is presented by the zocecial
apertures. These, generally, instead of being placed in longitudinal furrows)(as
128 THE PALEONTOLOGY OF MINNESOTA. :
(Rhinidictya.

is usual in the genus), are oblique and inclosed by a strongly elevated peristome,
highest at the posterior side. They manifest further a tendency to arrangement in
transverse or diagonal rows. The result is quite unlike what is to be expected in
Ehinidictya, and reminds one more of certain species of Cystodictya. Thin sections,
however, demonstrate that this is merely a case of superficial resemblance and not
of true relationship. On the contrary these prove, as is already clearly enough
shown at the growing extremities of the branches, that we are dealing with a true
Rhinidictya with affinities to R. mutabilis too close to admit of even specific distinc-
tion. Indeed, it is not improbable that the variety represents merely an unusual
condition of senility. Still, the interior, as exhibited in the sections at hand, has one
feature that may be accepted as corroborating my.present estimation of the form.

Plate VI, fig. 2, represents a portion of a tangential section showing, besides one
of the solid axillary macule, that the minute interstitial tubuli are exceedingly
numerous, there being often three longitudinal rows between adjoining zocecia.
Figure 3 of the same plate presents a portion of a vertical section of the same speci-
men. This compares very nearly with figs.5 and 12 (pl. VI) prepared from old exam-
ples of the typical form. The absence of horizontal lines in the lower part of the
walls may be the result of imperfect preservation.

This species, especially in its typical form, is to be regarded as closely allied to
R. nicholsoni Ulrich (Jour. Cin. Soc. Nat. Hist., vol. v. p. 170, pl. viii, figs. 6, 6a, 6b;
1882). Without taking into account certain slight though recognizable internal dif-
ferences, that species is distinguished by its narrower, more strictly parallel, and less
frequently bifurcating branches, the obliquity of its zocecial apertures, and the lesser
elevation and rigidity of the transverse interspaces. A nearer congener, perhaps, is
the R. basalis (Stictopora basalis Ulrich, op. cit., p. 169, plate viii, figs. 4 and 4a), but
the very frequent bifurcation of the zoarium characterizing that species serves to
distinguish them at a glance.* For comparisons with R. trentonensis, f. fidelis, and
other species described in this report see under descriptions of each.

Formation and locality.—The typical form is extremely abundant in the middle and lower beds of the
Trenton shales about Minneapolis and St. Paul, Minnesota. It occurs in these beds, but much less
abundantly, also at Cannon Falls, Lanesboro, Fountain, Preston and other localities in the southern part
of the state, and at Decorah,Iowa. The var. major is fairly abundant at the three localities first named, but
the Cannon Falls specimens are less robust than usual. From the Galena shales at Cannon Falls, I have
identified with the species something over forty fragments. In these, however, the zocecial apertures are
more oblique than usual. Respecting the Kentucky form, which I have heretofore referred to this species
(14th Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 67, 1886), I prefer to await further investigations before
expressing a conclusive opinion. This course seems the wisest also with respect to similiar forms from the
Trenton rocks of Illinois, Tennessee, New York, Vermont and Canada. ;

Mus. Reg. Nos. 5938, 5939, 5941, 5956, 5957, 7597, 7599, 7606, 7621, 7663.

*A very good illustration of the necessity of thin sections for the determination of the generic relations of these bifoli-
ate Bryozoa is furnished by my 1882 work on them in the publication cited. Had they been prepared of all the species therein
defined. I would not have fallen into errors that now appear only too obvious. There I placed, for instance, Pachydictya
acuta Hall, sp., Cystodictya gilberti Meek, sp., and Rhinidictya basalis under Stictoporu, while Rhinidictya was founded, correctly
enough, upon both external and internal peculiarities of R. nicholsoni. With sections I could scarcely have failed in deter-
mining the true position of these four species.

 
Rhinidictya ] BRYOZOA. 129

RuInIpIcTyA PAUPERA Ulrich.

PLATE V, FIQS. 19-21.

Stictopora paupera (part.) ULRIcu, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 69.

Zoarium usually less than 30 mm. high, consisting of narrow parallel-sided
branches, dividing dichotomously at intervals of from 4.0 to 12 mm. Near the base
the intervals are usually less than 6.0 mm., but further up the prevailing distance
between bifurcations is about 8.0 or 9.0 mm. The width of the branches is fairly
constant, deviating but little either way from 1.3 mm. Their thickness has not been
noticed to exceed 0.5mm. Zocecia with nearly direct oblong apertures, their shapes
varying with age from subquadrangular to elliptical. Interspaces rather narrow,
or of moderate thickness. Zocecial apertures usually in ten or eleven rows, but eight
or nine and twelve rows often occur just after and before bifurcations. The central
five or six rows are arranged between raised longitudinal lines, minutely granulose
when perfect, while the two or three rows on each side are, besides being slightly largér
than usual, directed obliquely outward. Five of the central rows in 0.7 or 0.8 mm;
measuring lengthwise along same eighteen or nineteen apertures in 5.0 mm. Internal
structure very much as in young examples of R. mutabilis Ulrich.

In the above diagnosis I have restricted my observations to the Minnesota form
occurring in the upper division of the Trenton shales at St. Paul and Cannon Falls.
This form should be regarded as the type of the species, and, pending further investi-
gations, the wisest course seems to be to restrict the use of the name to it. The
Kentucky and Tennessee form, occurring in the shaly upper member of the Trenton
group in those states, which I have referred to this species (loc. cit.), is now regarded
as distinct and next described as FR. neglecta. I have two specimens from the “ Phyl-
loporina beds” at St. Paul that are exceedingly like, if not identical with the latter,
but so far it has not been found in the shales above these beds, nor in the Galena
limestone division of the Trenton in Minnesota. But several examples collected
from the Galena shales at localities near Cannon Falls, seem to be identical with the
Canadian form referred to R. paupera in 1886. A very fine example, with branches
spread over a space 50 mm. wide by 75 mm. long, collected at Ottawa and kindly
given to me by Mr. Walter R. Billings, causes me to doubt the strict propriety of that
reference. -This specimen shows that the Canadian form agrees with typical B. pau-
pera in this, that the number of zocecial apertures in 5 mm., measuring lengthwise,
is eighteen to nineteen. Continuing our comparisons, however, we find the follow-
ing differences: (1) the apertures are smaller and rounder, and have a more distinct

-9
130 THE PALEONTOLOGY OF MINNESOTA. centers,

peristome ; (2) the interspaces on the whole are thicker, while the elevated lines
enclosing the depressed quadrangular spaces in which the apertures are situated, are
sharper ; (3) the arrangement of the apertures between longitudinal lines prevails
throughout, there being no oblique rows; and (4) while’ the width of the branches is
about the same or greater (the average is very nearly 1.5 mm.); there are only seven
to nine rows of cells instead of ten to twelve. In all these respects, however, the
Canadian form agrees more closely with R. neglecta, but before I commit myself def-
initely upon the matter of their true relations I shall want to institute careful
comparisons of their respective internal characters—a step that I am not yet pre-
pared to make. Still, in the meantime, it may be desirable occasionally to refer to
the Canadian form, in which case a distinctive appelation would be convenient. I
propose, therefore, the provisional designation Rhinidictya neglecta, var. canadensis.

Comparing R. paupera (sens. strict.) with other species of thé genus, we find that it
is distinguished from R. mutabilis by its smaller zoarium, narrow and more frequently
dividing branches, more numerous zocecia in a given space, and the greater differen-
tiation in the direction of the central and marginal zocecial apertures ; from R. trenton-
ensis and R. nicholsoni in much the same features, though in a different degree. To
them is to be added, for the former, that its zocecial apertures are not only much
larger, but more nearly quadrate or hexagonal, with the longitudinal ridges between
them nearly or quite obsolete ; and for the latter, that its zocecial apertures are
more oblique. AR. exigua is very close, differing mainly in its narrower branches and
less oblique arrangement of its zocecial apertures in the marginal rows. FR. minima
has thicker and more ornamental zoccial interspaces, and differs internally in hav-
ing the superior hemiseptum well developed.

Formution and locality—Not uncommon in the upper third (‘‘ Phylloporina beds”) of the Trenton
shales, at St. Paul and south of Cannon Falls, Minnesota, and Decorah, Iowa. Probably also in the
Galena at Neenah, Wisconsin. :

Mus. Reg. Nos. 5935, 7564, 7612.

RHINIDICTYA NEGLECTA, 7. Sp.
PLATE V, FIGS. 22-25.

Stictopora paupera (part.) ULRICH, 1886, Fourteenth Ann. Rept. Geol. Nat. Hist. Sur. Minn, p. 69.

Zoarium small, branches dividing dichotomously at intervals of from 4 to 7 mm.,
rather convex, the margins parallel, not very sharp, and with the non-celluljferous
border variable. Width of branches rather constant at about 1.5 mm. Zocecia’ in
eight to eleven ranges, the usual number nine, with rather small, elliptical ; oblique
apertures, about seventeen in 5 mm. lengthwise, and 6 in 1 mm. transversely. In
most cases all the apertures are directed longitudinally or parallel with the edges
Rhinidictya.] BRYOZOA. 131

of the branches; in others, however, those forming the marginal row on each side
may be turned slightly outward. Interspaces comparatively thick, less ridge-
shaped than usual, often slightly zigzag, with the range of granules well developed.

Internal structure chiefly diagnostic in vertical sections. These show that the

primitive or prostrate cell is comparatively elongate, and that at the turn into the
“vestibule” the wall is merely sharply curved and not angular, as in R. mutabilis.
_ Associated with this species is a larger form, agreeing in all other respects quite
closely with it. At first I thought it identical with R. mutabilis, and so figured it in
1890 (Ill. Geol. Surv. Repts., vol. viii, p. 304, fig. 2, d, f, and g). At present [ should
prefer regarding it as a variety of 2. neglecta. For the Canadian variety of this
species see remarks under R. paupera.

Compared with other species, RF. nicholsoné will be found to have grown differ-
ently, the bifurcation of the branches being much less frequent ; the zoccial aper-
tures are’also more oblique, and vertical sections quite different.. R. mutabilis has
wider branches, more direct zocecial apertures, and different vertical section.

Formation and locality.—Not uncommon in strata equivalent to the Galena limestone of the North-
west, at Frankfort, Kentucky, and several localities in Boyle and Mercer counties of that state. Also in
rocks of the same age at Nashville, Tennessee. Two fragments supposed to be identical with these
Kentucky and Tennessee specimens were collected at St. Paul from the upper shales.

Mus. Reg. No. 8104.

Rarnipictya exiaua Ulrich.
PLATE VIII, FIGS. 6-10.

-Rhinidictya exigua ULRICH, 1890. Jour. Cin. Soc, Nat. Hist., vol. xii, p. 184, fig. 9.

Zoarium bifoliate, small, growing from an expanded basal attachment. Lower
portion of branches subcylindrical, with the zocecial apertures here largely filled with
a smooth solid deposit of sclerenchyma. Above the first bifurcation the branches
have become acutely elliptical in cross-section, their width varying from 0.5 mm. to
1.2 mm., with parallel margins, the edges sharp, but in no case seeming to have
more than just an appreciable non-celluliferous border. Zocecia in from three to
seven rows on each face, their apertures, in the usual state of preservation, appear-
-ing as impressed, nearly direct, subelliptical or subquadrate, those in the central
rows 0.2 mm. long by 0.1 mm. wide, those in the marginal row on each side of the
branch sometimes a little larger and often directed somewhat obliquely outward ;
all regularly arranged longitudinally, seventeen or eighteen in 5 mm., and separated
from each other by rather thin, seemingly smooth interspaces, the latter forming
slightly elevated longitudinal ridges. In the specimens originally described and
figured, the apertures are somewhat obscured by remains of the shaly matrix, but
with several fragments lately discovered among my material from Fountain, Minn.,
132 THE PALEONTOLOGY OF MINNESOTA. cauaiisias:

this is not the case. The latter are also exceptionally well preserved and show that
the apertures are really rather strongly oblique, with a slight “lip” at the posterior
border. Not in these specimens, even, have I detected satisfactory evidence of the
presence of the row of granules on the longitudinal ridges usual in species of this
genus. Yet, as is shown by thin sections, the minute inter-zocecial tubuli, whose
superficial extension forms the granules, are developed in the usual manner.

The obliquity of the zocecial apertures allies this species to the larger R. nichol-
soni, but not closely enough to cause confusion between them. The zocecia are
larger in that species, there being thirteen to fifteen where we have seventeen to
eighteen in this form. It also resembles R. paupera and R. minima, but they are dis-
tinguished : the first by having more ranges of zocecia with the apertures in several
of the marginal rows on each side of the branches oblique; the second by its smaller
zocecial apertures and much wider granulo-striate interspaces.

Formation and locality.—Comparatively rare in the lower third of the Trenton shales at Minneap-
olis, St. Paul and near Fountain, Minnesota.

Raryipictya minima Ulrich,
PLATE V, FIGS. 13-18.

Rhinidictya minima Utricn, 1890. Jour. Cin. ‘Soc. Nat. Hist., vol. xii, p. 183, fig. 8.

Zoarium small, branches 0.8 to 1.2 mm. wide, commonly 1.0 mm., bifurcating at
intervals of 2or3 mm. Zocecia in five or six longitudinal rows, increasing to seven,
eight, or nine before bifurcation takes place; sixteen in 5 mm. lengthwise. Size and
shape of apertures, and character of interspaces, varying with age. The enlarged
figures on plate V represent the usual appearance of the oldest examples. In these the
zocecial apertures are small and narrow-elliptical (about 0.11 mm. by 0.06 mm.) and the
interspaces very wide, with the granulose ridges projecting but little above the level of
the peristomes surrounding the apertures. Under a glass of low power the interspaces
appear as rather flattened, and marked with straight or slightly flexuous longitudinal
strie. Under a higher power the striz resolve into rows of small papilla, with one
continuous series, a little stronger than the others, separating the apertures into
longitudinal rows, and one or two short series in the slightly depressed spaces
between the ends of the apertures. When in a good state of preservation, a row of
granules, rather smaller than the others, is found to crown the peristomes as well.
These were overlooked in drawing fig. 15. In younger examples the principal longi-
tudinal ridges are relatively higher, causing the zocecial apertures, which in these
cases are wider, and the intermediate spaces to appear as set in shallow channels,
Not infrequently the peristomes of succeeding zocecial apertures are connected in a,
Rhinidictya.] BRYOZOA. 133

manner causing the transverse interspaces to appear as bearing three longitudinal
strie or rows of granules. Margin of branches acute, the non-celluliferous band
rather wide and occupied by one or more lines of papille.

Of internal characters it will suffice to mention that there is a well-developed
superior hemiseptum, and a greater number of median tubuli in the end spaces
between the zoccial apertures (see fig. 18) than in any other species known to me.

This pretty little species is not likely to be confounded with any of the preced-
ing, unless it be with R. exigua. But the surface characters, especially when well
preserved, are so very dissimilar that confusion, even in that case, is inexcusable.

Var. MODESTA 7”. var.

PLATE V, FIG. 17,

Under this subordinate name I propose provisionally to classify an associated
form, differing in some respects constantly from the typical variety. Both are rep-
resented by numerous specimens, with no question in any case as to where each
belongs. They agree, however, too closely in the more important elements of struc-
ture to admit of specific separation. Except in the case of subsequent discoveries in
other regions proving the supposed new variety to hold its own geographically, the
above degree of separation seems to me sufficient. My studies of the paleozoic bifo-
liate Bryozoa have taught me to distrust mere deviations in the width of the branches
as being good specific characters. |

In the variety the branches are wider, the width varying from 1.7 mm to 3.0 mm.,
the zocecial apertures larger, and the interspaces correspondingly narrower. Still, the
number of apertures in 5 mm., measuring lengthwise, is, as in the typical form, about
sixteen. In the best preserved specimens the superficial characters resemble those
of young examples of typical minima very closely, the chief difference being that the
zocecial apertures, as already stated, are larger, and the non-poriferous band gener-
ally wider and grano-striated obliquely instead of longitudinally. The strize also
project slightly beyond the edge. causing the latter to be minutely serrate.

When the drawings for this species were prepared I possessed, unfortunately,
only a few specimens. The number was subsequently greatly increased by pickings
from washings of shales from the original locality, kindly sent me by Mr. W. H.

Scofield, of Cannon Falls.

Formation and locality.—Galena shales, near Cannon Falls, Minnesota; associated with species of
Nematopora, Arthropora armatum, Diastoporina flabellata, and other small Bryozoa characterizing the

horizon,
Mus. Reg. No. 8105. Var. modesta, 8106.
134 THE PALEONTOLOGY OF MINNESOTA. Tea
[Rinidictya.

Raripictya Fipeyis Ulrich.
PLATE VI, FIGS. 7, 7a, 7b AND 8.

Stictopora fidelis (part), ULRicH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 68.

To save repetition it will suffice to say of the external characters of this species
that they are exceedingly like those of the next described R. trentonensis, a slightly
greater width of the also more nearly quadrangular zocecial apertures, being rather
inconspicuous differences.

In tangential sections the deepest parts show the prostrate portion of the zoccia
lying on each side of the mesial laminew. The latter themselves may be shown as
in fig. 7b with the inclosed “median 'tubuli.” These horozontial tubuli seem to con-
nect with the vertical sets that form series separating the rows of zocecia. At first
the zocecia appear as simple quadrangular spaces, their width equalling about half
of the length. In the next stage these spaces are divided by a line, transversely in
the central rows, and obliquely upward in the marginal ranges. This line represents
the incurving superior hemiseptum, which is developed to an unusual degree in this
species. In the stage immediately succeeding, the posterior half is covered, while
the open anterior part is gradually reduced in width till it assumes the elliptical
shape commonly presented by the “vestibular” portion of the zocecia. From now
on to the surface, the distance depending upon the age of the specimen, the section
exhibits little if anything to distinguish it from similar sections of other species.
There are rows of subelliptical apertures separated by thick interspaces, and between
the rows a dark, faintly flexuous line, which, when carefully examined, is found to
contain a series of minute pores.

Vertical sections are highly characteristic, especially when they have been care-
fully prepared and show the primitive region of the zocecia in a satisfactory manner.
The anterior side of the zocecial cavity is almost straight from the mesial lamina to
the superficial aperture. The posterior and upper side is concave and the curve
produced in front into a strongly developed hemiseptum, projecting over half the
distance toward the base of the anterior wall. An occasional complete diaphragm-
like structure may be detected crossing the tubular vestibule. All of these char-
acters are shown very well in fig. 8.

As has been stated, it is not an easy matter to distinguish this species, by means
of external characters alone, from R. trentonensis, and until the observer has become
thoroughly familiar with the various forms of this genus occurring in the Minnesota
rocks, he is cautioned to secure the evidence of thin sections before he places much
confidence in his identification, of this species, at any rate. The strongly developed
Rhinidictya.] baer: 185

superior hemiseptum will distinguish the sections at once from those ot all other
species except R. minima. That species occurs at a higher horizon (Galena shales),
grew differently, has smaller elliptical zocecial apertures and much thicker, as well
as quite differently marked interspaces.

Formation and locality.—Rare in the lower third of the Trenton shales at Minneapolis, Minnesota.
Mus. Reg. Nos. 5986, 5937. i

R#INIDICTYA TRENTONENSIS Ulrich.
PLATE VI, FIGS. 14-18; PLATE VII, FIGS. 6-9.

Dicranopora trentonensis ULRICH, 1882. ‘‘ Amer. Pal. Bry.,” Jour. Cin. Soc, Nat. Hist., vol. v,
p. 160, pl. 6, figs. 15, 15a.
Stictopora fidelis (part.) ULRIcH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 68.

Zoarium branching dichotomously at intervals of from 8 to20 mm. Branches 2
mm., or a little less, wide, sharp-edged, the non-poriferous margin very narrow
Zocecia in from eight to eleven ranges, nine or ten the commonest numbers. Aper-
tures nearly direct, comparatively large, of elliptical, subquadrate or hexagonal form,
with sixteen, rarel yseventeen,in 5 mm. longitudinally, and five in 1 mm. transversely;
those forming the marginal row usually a little larger than the average and directed
slightly outward. Interspaces thin, apparently without granules, the longitudinal
ones but little, if at all, elevated over those running transversely, the former gene-
rally 4 little zigzag in their course.

In tangential sections dividing the zoarium just beneath the surface, the inter-
spaces are moderately thick, and contain a line of very minute pores running length-
wise between the rows of cells. Here the zocecia, or rather their “vestibular” por-
tions, are elongate-elliptical, but at a deeper level, where the section cuts down into
the primitive portion of the zoarium, they have the usual oblong-quadrate, or sub-
rhomboidal shape. In one of the sections showing this region (see pl. VI, fig. 18)
a row of “median tubuli” is distinctly visible in the transverse partitions.

Vertical sections remind us much of &. nicholsoni and R. grandis, in this, that the
interspaces or walls are rather thin, and that there is not even a sign of a superior
hemiseptum at the base of the “ vestibule,” the walls being merely thickened a little
abruptly. In sections of thick examples a complete diaphragm may cross the tubes.
In such cases it is common to find each half of the zoarium, in part at least, to con-
sist of two superimposed layers of cells.

“A re-examination of the Tennessee type of this species has shown conclusively
that it is not a Dicranopora but a Rhinidictya, with relations to RB. nicholsoni and R.
grandis, its systematic position being nearly intermediate between them. From the
136 THE PAL
EONTOLOGY OF MINNESOTA. reituaroege:

first of those species it differs mainly in its wider and nearly direct zocecial aper-
tures and narrow interspaces, these being also without surface granulations so far
as observed. Still, some of the Minnesota specimens referred here resemble &.
nicholsoni more closely than do the Tennessee types. It is therefore not improbable
that more detailed comparisons than I have found time to make may show that, as
T believed'in 1886, R. nicholsoni also is represented in the Minnesota strata. R. grandis
is readily distinguished by its wider branches and larger cells. R. pediculata likewise
seems closely related, but its peculiar growth and somewhat wider branches will, it
is believed, serve to separate them. Lastly, R. fidelis so closely resembles this species
in its external characters that I am at a loss to point out really serviceable distin-
guishing features. Asa rule the zoccial apertures of R. trentonensis are a trifle nar-
rower and less often of quadrate shape. Comparing their internal characters, we
at once notice a decided difference in the inner part of the zocecia where that species
presents a well developed superior hemiseptum. This is a point of such importance
that I am obliged to view the two species as widely distinct.

Formation and locality‘ Glade” limestone (Birdseye) at Lebanon, Tennessee; lower third of
Trenton shales at Minneapolis, Minnesota. Rather rare. It has also been collected by Mr. C. Schuchert
in the “‘ Lower Blue beds” at Janesville, Wisconsin, and Rockton, Illinois.

Mus. Reg. Nos. 7549, 7560.

RHINIDICTYA GRANDIS 7. Sp.

PLATE V, FIGS. 11 and 12; PLATE VI, FIGS. 19 and 20.

Zoarium bifolate, large, branchy, the branches flattened, 2.5 to 3.5 mm. wide, the
edges obtuse, with the non-poriferous margin of moderate width. Zocecia in from
eleven to fifteen alternating rows, with large, almost direct, slightly oblong, hexa-
- gonal apertures, fourteen or fifteen in 5 mm. longitudinally, and nine of the central
rows in 2mm. transversely. Interspaces thin, without papille, ridge-shaped, sloping
down into the apertures from the summit, the latter reaching to about the same level
in both the cross and longitudinal partitions. In conforming with the hexagonal
shape and alternate arrangement of the zocecial apertures, the longitudinal walls
usually take a decidedly zigzag direction. In the marginal rows the apertures are
commonly more or less irregular in shape, size and arrangement. An occasional
small cell may be noticed.

In vertical sections the comparative erectness of the zocecia is to be noticed;
also the shape of the walls, ‘These show no sign of a superior hemiseptum, though
a slight angularity is often perceptible at the turn into the vestibular region.
Rhinidictya. j BRYOZOA. : 187

Tangential sections give a good idea of the unusual size of the zocecia. When
the section cuts deeply the prostrate portion of the cells is shown. Here they have
the usual characters—thin walls, the longitudinal ones straight, the transverse ones
at right angles to them in two or three of the central rows, and directed obliquely
upward in the lateral series, the obliquity increasing with each successive row. Just
beneath the surface the apertures are elliptical, with a faint line about them, while a
series of exceedingly minute dots, or a fine double line instead, passes longitudinally
through the interspaces.

The large size of the zocecial apertures distinguishes this species from all others
of the genus known to me. Their hexagonal shape, and the absence of longitudinal
ridges are two more features that may be relied on in separating it from such species
as R. mutabilis, R. nicholsoni, R. fidelis and R. neglecta, but R. pediculata and R. trenton-
ensis approach it in these respects. The last is, I believe, its nearest congener, but is
distinguished readily enough by its narrower branches and smaller zocecia.

Formation and locality—The types are from the Birdseye horizon of the Trenton formation at
Dixon, Illinois. Other examples were noticed in Wisconsin material collected for the State Museum by
Mr. Charles Schuchert and sent me for identification. All the specimens are from the ‘Lower Blue
Beds” of the Wisconsin geologists, in which the species is sometimes associated with R. trentonensis. Mr.
Schuchert’s localities are near Beloit, Mineral Point and Janesville.

Mus. Reg. Nos. 7548, 7554, 7593, 7594,

RHINIDICTYA PEDIOULATA 1”. Sp.

PLATE VII, FIGS. 1-5.

Zoarium bifoliate, apparently growing to but little more than 25 mm. in hight.
It begins with a small expansion, by means of which it was evidently attached to
foreign bodies. Arising from this is a small and short, rounded, subsolid and striated
footstalk, that soon flattens and spreads into rapidly bifurcating branches, all spread-
ing approximately in the same plane. The branches have an average width of about
3.0 mm., are very thin, with unusually sharp edges, wide and obliquely striated non-
poriferous margin.* Zocecia in from eleven to fourteen ranges, the usual number
twelve, with the outer row on each side irregular in their arrangement, larger than
the average, and directed obliquely outward. In the central rows the apertures are
commonly elliptical, or subangular, and sunken into oblong hexagonal spaces,
bounded by thin walls, of which the lateral ones form slightly zigzag, low ridges.
The last feature, however, is to be seen only in the best preserved examples, those in
the usual condition seeming to have the interspaces rising to the same level on all sides
of the aperture. Measuring lengthwise along the central ranges fifteen or sixteen

—

*The latter is not shown in fig. 5, (pl. VII) the drawing having been made from a weathered example.

 
138 THE PALEONTOLOGY OF MINNESOTA.
[Eurydictya.

zocecial apertures are to be counted in 5 mm., while twelve rows occur on a branch
3.0 mm. wide, on which the non-poriferous borders occupy space amply sufficient,to
accommodate another row on each side.

Internal characters not observed, the process of fossilization having been too
unfavorable to preserve the minuter details of structure.

The small footstalk, rapid spreading of the zoarium, and the wide marginal
space, are the characters relied upon in distinguishing this species. In other respects
the species is very near R. trentonensis and R. grandis.

Formation and locality.—A]l the specimens seen were collected by the author from the lower lime-
stone of the Trenton formation, at Minneapolis, Minnesota.

Mus. Reg. No. ?5934.

Genus EURYDICTYA, Ulrich.

Eurydictya, ULRICH, 1889. Miller’s N. Amer. Geol. and Pal., p. 301; 1890, Geol. Surv. Tl1., vol. viii,
pp. 389 and 520.

Zoaria bifoliate, consisting of broad, simple or irregularly divided expansions,
the surfaces of which exhibit more or less conspicuous, though usually small, macule
or monticules. Zocecia of the same type as in Rhinidictya.

Type: LE. montifera ‘Ulrich, 1890. Geol, Surv. IIL, vol. viii, p. 521.

This genus was established for the reception of a small group of Lower Silurian
species that, though intimately related to Rhinidictya, Ulrich, it seemed desirable to
distinguish from that genus. The broad and undefined zoarial expansion pertaining
to the several species gives them a very different aspect from that presented by the
narow, parallel-margined, and regularly branching stipes so strictly adhered to by
all the true species of Rhinidictya. That intermediate forms occur is true, nor can
we doubt that the dividing line between the two genera will continually grow more
shadowy with the discovery of new species. » But, as that difficulty is encountered
by the systematist throughout all organic nature, it cannot be regarded as a bar to
the formation of generic groups, because, theoretically, if the course were carried to
its logical conclusion, all necessity for classification would cease. Some recognition
of obvious departures from a type is necessary, and in the present incompleteness of
our knowledge the only satisfactory plan to accomplish this is to adhere strictly to
the binomial nomenclature. In this declaration I am to be understood as aiming at
subgeneric rather than varietal designations.

Eurydictya multipora (? Hall’s sp.), the only species of the genus so far known to
occur in Minnesota, is the least typical of the genus. In shape and structure of its
end walls the species approaches Phyllodictya varia. The type of the genus, E. mon-
tifera, may be looked for in the upper beds of the Hudson River group in Fillmore and
other counties in the southern part of Minnesota where that horizon is exposed.
BRYOZOA. 139

Eurydictya.]

Evrypictya MuLTIPoRA ? Hall, sp.
PLATE VI, FIGS. 9-11; PLATE VII, FIGS. 24 and 29-31; PLATE XIV, FIGS. 9-11.

? Phenopora multipora HALL, 1851. Geo. Lake Sup. Land Dist., vol. ii, p. 206.
Pheenopora (?) multipora ULRIicH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 171.
Eurydictya multipora Uricu, 1890. Geol. Surv. IIL, vol. viii, p. 520. (Referred to new genus only.)

Zoarium forming irregularly divided wide fronds, 6 to 20 mm. in width, or simple
undulating expansions, or a combination of the two. The Minnesota example figured
on plate XIV is a fragment of a slightly undulating expansion, 0.7 mm. to 1.5 mm.
thick, that must have been no less than 20 mm. wide. The others are of less width,
and one (plate VII, fig. 24) deviates so widely from the ordinary growth that it was
at first believed to belong to Rhinidictya mutabilis var. major.

Surface with irregularly distributed small macule, often very inconspicuous and
scarcely interrupting the regularity of the longitudinal ridges. In other cases they
may appear as smooth solid spots, fully 1 mm. in diameter. Asa rule they give one
the impression of a variable number of elongate zoccia filled with a solid deposit of
calcareous material. Zocecial apertures subelliptical, more or less oblique, (generally
more so than in fig. 11, plate XIV) with a slight peristone, strongest at the posterior
margin, arranged between rather prominent, granulose, longitudinal ridges, seven-
teen or eighteen in 5 mm.; also in curved diagonal series, but these are never very
regular and frequently turn into transverse rows. Measuring transversely, from
twenty-three to twenty-six of the longitudinal rows may be counted in 5mm. The
width of the interspaces is usually about equal to the diameter of the apertures.
When the latter are partially filled with the clayey maxtrix, they may appear as of
subquadrate shape, with the interspaces thinner than usual. In the narrow or basal
part of the fronds, the spreading edges are sharp, non-poriferous, and striato-
granulose, while several of the marginal rows of the zocecial apertures may be
directed obliquely outward.

Vertical sections show that the primitive cell is rather high, short, and has thin
walls. These curve over it to a point marking the beginning of the vestibular por-
tion of the tube, when they bend sharply outward. At the same time the interspaces
(walls) are greatly widened, and three to five shallow vesicles are developed in direct
sequence. Above these the interspaces are solid and seemingly structureless, if we
except a dark line running lengthwise through them. No diaphragms observed.

Tangential sections may present one or all of three distinct phases or stages in
the development of the zoarium. Their exhibition depends upon the distance from
the median lamin at which the zocecia are cut by the section. In the first or deep-
est part of the section, the zocecia are quadrate, thin-walled, and arranged in regular
140 THE PALEONTOLOGY OF MINNESOTA ;
[Euridictya

rows between longitudinal plates. The end or transverse partitions appear less sharp
than the longitudinal lines, are generally a little curved; and cross the spaces at either
a right angle to the direction of the growth, or somewhat obliquely. In the latter
case the primitive cell is subrhomboidal in shape. In the succeeding stage we see
the structure immediately following the formation of the original aperture, 7. e., the
beginning or lower part of the vestibular portion of the zoarium. Now the zoccial
cavity is rounded, of elliptical shape, with a thin ring-like wall, generally in contact
with the longitudinal plates. The latter appear usually as dark structureless lines
separating the rows of cells. The end spaces, in part at least, may be empty (2. e,,
filled with clear calcite) thus indicating the presence of interstitial vesicles. In
the third or superficial stage, the interstitial vesicles have been filled with solid tissue
and the diameter of the zocecial cavities generally reduced a little by a thin internal
deposit, while the dark longitudinal lines are now clearly resolvable each into a
crowded row of exceedingly minute tubuli. :

Some of the St. Paul specimens look very much like wide examples of the large
variety of Rhinidictya mutabilis, but after one becomes familiar with the peculiarities
of each, it is not difficult to distinguish them. In the first place the zoaria of the var.
major have always an aged appearance, being heavy, with subparallel, rounded edges,
thick interspaces, and correspondingly narrow zocecial apertures. The small ,speci-
mens of E. multipora, on the contrary, are thin, sharp-edged, oftener and more irreg-
ularly divided, and with comparatively thin interspaces, When we compare thin
sections the differences are as shown on plate VI, by figs. 1 and 9, 6 and 10, and 11
and 12.

Both E. calhounensis Ulrich, and E. montifera Ulrich, have a well developed
superior hemiseptum, but no interstitial vesicles. In other respects the first is
rather closely simulated by the present species. There is no associated species with
which EL. multipora is likely to be confounded. The Rhinidictya var. major is not
found, as far as known, so high in the shales, being restricted apparently, like Phyl-
lodictya varia, another wide bifoliate form, to the middle division of the Trenton
shales.

This species, as above cited, was described by me from Kentucky specimens.
Since then 1 have found it in Tennessee, and in 1885 a single example in the Minne-
sota State collection proved to belong to the same species. Two years later Mr.
Schuchert and the writer secured about ten specimens at St. Paul.* Respecting the
specific identity of all these specimens with the originals of Hall’s Pheenopora multi-
pora, I should say, that I am still of the opinion expressed in 1882, but having since

 

 

*During the past two weeks (to April 10th, 1892,) the writer secured no less than fifty specimens at St. Paul.
141
Phyllodictya.] BRYOZOA.

then learned to esteem caution, the present less positive stand on the question will
suffice till we have been informed of the minute structure of Hall’s types. These
were derived from the northern part of Wisconsin, and if they prove to be identical
with the specimens here described,*a considerable extension of the geographical
range of the species will result. The species is an important one too, in being
highly characteristic of one horizon.

. Formation and locality—In Minnesota known only from the upper third of the Trenton shales, at
St. Paul. In Kentucky, rather common in the shales above the ‘‘ Modiolopsis beds.” In Tennessee it
holds the same horizon (Safford’s Middle Nashville Series) at Nashville.

Mus. Reg. No. 5942.

Genus PHYLLODICTYA, Ulrich.

*

Phyllodictya, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 153; MILLER, 1889, North Amer.
Geol. and Pal., p. 315; UnRicu, 1890, Geol. Surv. Tll., vol. viii, p. 390.

Zoaria bifoliate, Simple or iregularly branched, growing from an expanded basal
attachment. Zocecial tubes long, with complete diaphragms but no hemisepta; from
the central axis they bend outward very gradually, causing the apertures to be more
or less strongly oblique, with the posterior edge raised lip-like. Interspaces wide,
subsolid, transversed vertically by one or two rows of minute tubuli, which appear
as so many papille at the surface.

Type: P. frondosa Ulrich.

This genus requires more study before the relations to Eurydictya on the one
side, and Pachydictya on the other, can be determined and satisfactorily established.
The questions involved are rendered difficult of solution by the commingling of
characters found in Pachydictya splendens Ulrich. and P. firma Ulrich, of the upper
beds of the Hudson River group, and EKurydictya multipora (? Hall) of the Trenton
group. All three of these species have certain features in common that do not per-
tain to the more typical forms of either Pachydictya or Eurydictya. It is, however,
precisely in those characters that these species remind us of Phyllodictya.* Though
having an abundance of specimens of, at any rate the majority of the species, bear-
ing directly upon the points at issue, I have been obliged, chiefly because of a lack
of time, to defer pushing my investigations to a satisfactory conclusion. I realized
also that all partial studies of the group of bifoliate Bryozoa, and consequent rear-
ravgements of species, are only too likely to prove premature and faulty when the
full results of a complete study of the group shall have become available. For the
present it is sufficient to point out the obscure and perhaps weak spots in the classi-

fication now in use.

 

*Another genus presenting points of agreement with Phyllodictya is Ptilotrypa Ulrich, founded upon a single species
from the upper beds of the Hudson River group, But the absence of “median tubuli” in the latter is a difference of
such importance that the two genera must be regarded as widely distinct and as belonging to different families.
142 THE PALEONTOLOGY OF MINNESOTA.
LPhylodictya.

PHYLLODICTYA FRONDOSA ? Ulrich.

(Not figured,)
: e
Phyllodictya frondosa ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 174, pl. 8, figs. 11, lla
and 11b.

The name of this species occurs in the list appended to my preliminary report
on the Minnesota Bryozoa (Fourteenth Ann. Rep. Geol. Surv. Minn., p. 102; 1886).
The identification was based upon several small fragments, none of them in a con-
dition to afford satisfactory thin sections. Nor did any of the more numerous and
larger specimens of Phyllodictya collected subsequently for my own cabinet by Mr.
Charles Schuchert and others, as well as by myself, prove any better for that purpose.
I was, therefore, unable to verify the identification until last year, when I detected a
single well preserved fragment, about 15 mm. square, in a lot of fossils kindly given
me by Prof. C. W. Hall, of the State University. Both the superficial and internal
structure of this specimen, which was obtained too late to appear on the plates,
agrees closely enough with that of one of the original Kentucky types of the species.
Ordinarily, this would be quite sufficient to establish the identification of a species,
but in this case, a fact about to be mentioned causes me to use the question marks.
Recently I had occasion to prepare a set of thin sections of a specimen supposed to
belong to this species. These seem to differ so much from the original set, that one
of two things is evident: either I included two species in my original diagnosis of
P. frondosa, or the species is more variable in its internal structure than I supposed.
It is probable that the differences observed are only the result of age, but as I have
not had time to make the sections necessary to prove this, I thought it best to men-
tion the difficulty, leaving its removal to some future time. Before giving the fol-
lowing brief description of the Minnesota specimens, it would be well to mention
that the one received from Prof. Hall agrees best with the specimen represented by
fig. 11 of the original work on the species, while the resemblance to the specimen
that furnished the original thin sections and the enlarged surface view is much
less.* Also, that I now believe that none of the specimens catalogued by me in 1886
as P. frondosa really belong there. Most of them, perhaps all, are to be referred to
the new species P. varia. *

Zoarium leaf-like, 1.5 mm. thick; size unknown, only fragments having been
seen. At intervals of 3 or 4 mm. the surface presents smooth or grano-striate
solid spots, 1 mm. or more in diameter. These spots may be on a level with the
general plane of the surface, or slightly depressed. Zocecial apertures ovate, a little

 

*The new set of sections were prepared from an example like the first,
BRYOZOA. 148
Phyllodictya.]

drawn out anteriorly, with the posterior edge abrupt and slightly elevated, arranged
in straight or curved, diagonally intersecting lines, and, less obviously, in longitudinal
series, with about; seventeen in the former and twelve in the latter in 5 mm. Inter-
spaces separating the apertures in the diagonal rows narrower than the apertures,
while those between their ends may be wider and concave instead of rounded, with
the posterior rim extending up along their sides. When in a good state of preserva-
tion a row of minute papillz crowns this rim, and thus extends around the posterior
margin of the zocecial apertures and up their sides to the row belonging to the suc-
ceeding aperture. There are therefore two rows of these papille between neighbor-
ing apertures, but it is not uncommon to find the spaces between the apertures in
the diagonal rows too narrow for their full development, and then they are crowded
into an irregular single row. .

In vertical sections the zocecial tubes begin with a rather long prostrate cell
from which they proceed to the surface by a gentle outward curve ; the continuance
of this curve causes the apertural portion of the tube in old examples to be much |
more nearly direct to the surface than in their younger stages. In an average
example a line drawn from the aperture to the proxima] extremity of a tube forms
an angle of about 35 degrees with the central lamine. Complete diaphragms to the
number of five have been observed to cross each tube. Near the central axis the
walls are thin, but soon they begin to spread, admitting of the intercalation of from
three to five successive vesicles. Above these the interspaces are filled with solid
matter, seemingly structureless except for the minute dark tubuli traversing them
in a direction at right angles to the plane of the zoarium. These tubuli arise in a
dark line running along the posterior side of the tube.

Tangential sections show a considerable deposit of solid material on the inner
side of the tubes. This is scarcely to be described as ring-like, since it is not sharply
defined nor of equal thickness all around, being widest and rather indistinct anteri-
orly, and but illy distinguished at any point from the interspaces. The latter are
occupied by minute dark spots (median tubuli) in single or double rows, representing
and corresponding with the arrangement of the minute superficial papille described.

The above description is based almost entirely upon the specimen mentioned as
having been received from Prof. C. W. Hall. Its characters, as has been stated, agree
very closely with one type of P. frondosa, but not nearly as well with the other, pos-
sibly distinct form, originally united with it. Compared with P. varia, to which I
shall provisionally refer nearly all of the Minnesota specimens of Phyllodictya so far
geen, it will be found to differ in having thinner interspaces, and larger apertures,
with the diagonal instead of the longitudinal arrangement predominating. Further
144 THE PALEONTOLOGY OF MINNESOTA.
([Phyllodictya.

differences are to be found in the character of the interspaces, and in the shape of
the zoarium.

Formation and locality—Rare in the Trenton shales, at Minneapolis, Minnesota. The types of the
species are from the Birdseye limestone at High Bridge, Kentucky.

PHYLLODICTYA VARIA, %. Sp.
PLATE XIV, FIGS, 1-8.

Comp. Stictopora labyrinthica HALL, 1847. Pal. N. Y., vol. i, p. 50.

Zoarium variable, consisting of broad, leaf-like, thin expansions, either simple
or with irregular marginal incisions, or of wide branching fronds, with the edges
subparallel, sharp, and non-poriferous. At intervals of about 4 mm. the surface
exhibits subsolid, even or slightly depressed spots or “macule,” smooth when worn,
finely grano-striate as well as faintly channeled longitudinally when well preserved.
In the youngest examples these macule are small and sometimes scarcely distinguish-
able, but with age they seem to increase in size (compare figs. 2 and 7). The most
obvious and normal arrangement of the zocecial apertures is in longitudinal series,
twelve or thirteen in 5 mm., between delicate papillose ridges; but the general
aspect of the surface varies greatly in the specimens before me. Some of these dif-
ferences are doubtlessly due to, or exaggerated, by weathering and other accidental

“causes, yet others are as clearly changes consequent upon increasing age, and thus
are to be regarded as expressing different stages in the development of the zoarium.
In the youngest the zocecial apertures are very oblique, with a rim, strongly elevated
at the posterior side, and dying out at the sides or seeming to unite with the delicate
ridges separating the rows. This condition is represented in figs. 2 and 3. In later
stages the longitudinal ridges becomes indistinct, the interspaces flatter, the poster-
ior “lip” less pronounced, the apertures less oblique and, sometimes, a little smaller,
while in other cases, probably representing a weathered condition, they appear
larger, with the interspaces rounded. The longitudinal arrangement also becomes
less obvious but never, so far as observed, quite subordinate to the diagonal. This
may seem to have occurred over limited spots, especially when the macule are unusu-
ally large as in the specimen represented by figs. 6 and 7.

Only one specimen proved suitable for sectioning. This even failed to preserve
the minuter details of structure as well as was desired. So far as the internal char-
acters could be made out they are shown in figs. 4 and 5, excepting that by an ‘unac-
countable oversight the diaphragms were not drawn in the vertical sections. Each
tube should have shown one diaphragm crossing it at right angles at a point about.
midway between its aperture and the mesial line, -

“
Pachydictya.] BRYOZOA, 145

This species is closely related to a common form of the Birdseye limestone in
central Kentucky, which I regard as likely to prove identical with Hall’s Stictopora
labyrinthica, described from the some horizon in New York. But in the absence of
any knowledge of the interior of that species, it would be highly injudicious, surely
unwarranted, to assert their identity. Still, it is possible that even the Minnesota
form may be only a local variety of that species. However, the probability of that
supposition is so remote that I feel no hesitation in proposing the new name varia
for the form here described.

Formation and locality.—Restricted to the middle third of the Trenton shales at Minneapolis, Min-
nesota. A single example from about the same horizon at Cannon Falls.

Mus. Reg. No. 5953.

Genus PACHYDICTYA, Ulrich.

Pachydictya ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 152; FoERSTE, 1887, Bull. Sci. Lab.
Denison Univ., vol. ii, pt. ii, p. 162; MILLER, 1889, N. Amer. Geol. and
Pal., p, 313; ULRIcH, 1890, Geol.:Surv. Il., vol. viii, p. 390.

This genus, in its fullest sense, falls into three distinguishable, yet not entirely
natural sections, having precisely the same relations to each other as Rhinidictya
and Eurydictya, Cystodictya, Dichotrypa and Prismopora. These genera, being based
entirely upon zoarial deviations, are evident to the unassisted eye, and the micro-
scope is not necessary in distinguishing them. To be consequent, a similar splitting
up of Pachydictya is suggested, but such a course would be only too liable to lead to
misunderstandings, since we would be obliged, for the same reason, to follow the
plan to its logical conclusion in dealing with Pétlodictya and Phenopora, in which
precisely the same divisions, as well as others equally marked, obtain. It is, there-
fore, deemed sufficient for present needs to designate two of them with the non-
committal terms of Section a and Section b. The third, however, being a departure
in a more obvious and seemingly more important direction, is entitled to better
attention. For it the name Trigonopictya is proposed.

The following diagnosis embraces the characters of the two sections, but those
features that may be considered as especially characteristic of one or the other, are
indicated by the letter a or } in parentheses following the statements.

Zoaria bifoliate, consisting of irregular wide branches, large or small, and more
or less undulating, leaf-like expansions (a), or of narrow, subparallel-margined, and
dichotomously branching stipes (2). Margins acute, with a non-poriferous border,
obliquely striate or grano-striate. Surface with small macule and, about them or
taking their places, clusters of zocecia of more or less obviously larger size than the
asionally montiferous (7). In other cases (d) these clusters are repre-

average ; occ
—10 -
146 THE PALEONTOLOGY OF MINNESOTA.
' [Pachydictya.

sented by the marginal rows of apertures which are commonly of larger size, with
wider interspaces, and less regularly arranged than those of the central rows. Zocec-
ial tubes rising rather abruptly from the mesial laminz, the primitive cells with thin
walls, longitudinally arranged, of elliptical, semicordate, or subquadrate form, in
most cases partially separated from neighboring cells by small interstitial vesicles.
Toward the surface their walls are thickened, often ring-like, subelliptical in cross-
section, usually completely isolated, the interspaces solid excepting that they are
transversed by one or more, straight or flexuous, series of minute tubuli. One or
more (the number depends upon age of example) complete diaphragms in each
zocecial tube. Apertures usually elliptical, rarely subangular, the “closures” with a
subcentral small opening. Interspaces grano-striate, concave and forming a peri-
stome about the zocecial apertures, or thrown up into longitudinal ridges. Median
tubuli between the halves of the double mesial plate.

Type: PP. robusta Ulrich.

The distinguishing characters of section a, which includes the type of the genus,
are (1) the wide, palmate or foliar zoarium, and (2) the macule and clusters of large
zoccia. The section might be still further subdivided according to whether the
longitudinal arrangement of the zoccial apertures predominates, or that in diagon-
ally intersecting series. The latter would include the species robusta, everetti, foliata,
magnipora and hexagonalis, all, save the last, described by me from the lower beds of
the- Trenton formation; while the former would embrace the species occidentalis
Ulrich (upper Trenton), fenestelliformis (Nicholson), firma, gigantea, and splendens,
Ulrich (upper beds of Hudson River group), and species obesa and turgida, described
by Foerste from the Clinton rocks of Ohio.

In section }, the zoarium is narrow, and its margins subparallel, while the longi-
tudinal arrangement of the zocecia is always the predominating one. It seems that
maculz, or merely an unusual width of the interspaces, must always accompany the
clusters of large cells, and as the room was insufficient in these narrow zoaria for
their proper development, or, it may have been that their presence would have
interfered too greatly with the regular growth of the branches, they (the large cells)
are instead arranged along the margins, where we may assume, the necessary condi-
tions to have been afforded by the non-poriferous border, which is constructed essen-
tially upon the same principle as the macule.*

The following species are to be arranged under Section 6: acuta (Hall) fimbriata,
pumila, and triserialis, from the Trenton ; aleyone, arguta, and rustica, of Billings, from

 

*It is a fact worth remembering that as soon as the width of the zoarium of one of the paleozoic- bifoliate Bryozoa
exceeds 4 or 5 mm., a maculum or cluster of cells larger than the average is found a short distance beneath the axes of
bifurcation. A still greater increase and we have a row of macule or monticules along the center of the surface. Several
instances of this kind are illustrated on the plates accompanying this volume. (See plates VII and VIII.)
peepee BRYOZOA. 147

the Anticosti group; crassa (Hall), bifurcata (Van Cleve), emaciata (Foerste), farctus
(Foerste), and rudis (Foerste), from the Clinton, and scitula (Hall) from the Niagara."

In placing Pachydictya under the Rhinidictyonide I follow the course adopted in
my 1882 work on the “American Paleozoic Bryozoa,” (Jour. Cin. Soc. Nat. Hist., vol. v),
and more recently in the eighth volume of the reports of the Geological Survey of
Illinois, published in 1890. I have always had some doubt as to the strict propriety
of the arrangement, and the chief reason for its continance in the last work is found
in the fact that the genus agrees with Rhinidictya and all true genera of the family
in having “median tubuli.” Now that I am employing the classification for the
third time, it seems desirable to publish at the same time some account of my objec-
tions. At first I thought some of proposing a new family for Pachydictya and the
new. genus Trigonodictya, but was restrained from doing so by the fear that I could
not, in the present state of our knowledge, satisfactorily establish the distinctness of
the new family from the Rhinidictyonide. The difficulties are encountered when we

attempt to draw sharp lines between certain species of Pachydictya on the one side,
and Phyllodictya and Eurydictya on the other. Had I made the presence or absence
of diaphragms the test, I would very likely have struck the popular chord, but as I
know that test to be unreliable only too often when applied to groups of high rank,
I could not employ it before knowing more of its value in this particular case.

The suggested removal from the Rhinidictyonide is not caused through any
depreciation in the value of the character mentioned (median tubuli), but is founded
upon a better appreciation of certain features wherein Pachydictya and Trigonodictya,
and in a lesser degree also Phyllodictya, differ from the more typical members of the
family: Rhinidictya, Dicranopora, Goniotrypa, and Eurydictya. In all of the latter
the primitive or prostrate portion of the zocecial tube is of an oblong-quadrate or
rhomboidal shape, the thin wall of adjacent cells being, moreover, in contact with
each other on all sides. Nor are interstitial vesicles or mesopores present in any of
them with the single exception of Eurydictya. multipora (? Hall’s sp.). Diaphragms,
also, are very unusual, while a more or less well developed hemiseptum is common.
’ Finally, the interspaces, as shown in tangential sections, continue uninterruptedly
from zocecial cavity to cavity, there being no sharply defined ring-like wall around
the latter.

In Pachydictya, Trigonodictya and Phyllodictya, however, the hemisepta are never
present, but complete diaphragms seem to have been developed in all examples old
enough to have them. Tangential sections bring out peculiarities fully as striking
and important, but their statement should be premised with the admission that some
of them are but illy developed, possibly quite unrecognizable, in some of the species.

 

*I am convinced that severa], perhaps over half, of these nine Middle and Upper Silurian species are synonyms.
148 THE PALEONTOLOGY OF MINNESOTA.
, (Pachydictya.

Perhaps, the chief ones of the characters about to be mentioned, are those that have
resulted in the presence and early development of interzocecial spaces. These begin,
generally at any rate, the same as in the Cystodictyonidee and the bifoliate Fistulipor-.
ide (Meekopora Ulrich) at the basal (mesial) plate, causing the primitive cell of the
zocecial tubes to be in part separated from its neighbors, and to have a shape quite
different from that of the.Rhinidictyonide. Indeed, the resemblance to the semi-
cordate cell so prevalent among the Cystodictyonide, is often very striking. (See
plate IX, figs 8 and 18.) A common condition is when a small triangular interspace
has been cut off from each of two diagonally opposite corners of the primitive cell.
These interspaces increase in size and form shallow vesicles as growth proceeds, and
as soon as the tubes have assumed an erect position, they are completely isolated by
the superimposed vesicles. At the same time their walls become more or less
thickened and ring-like, and, from now on to the surface, the zocecial investment
remains, almost invariably, clearly distinguishable from the interspaces proper, the
sharpness of definition between them being in most cases even increased after the
interspaces have been filled with the usual solid deposit. These changes in the
zocecial structure are shown in the various figures:on plate IX.

In Phyllodictya and Trigonodictya, as well as in some of the small species of Sec-
tion b of Pachydictya, we have no positive evidence of the development of the inter-
stitial vesicles until after the zocecia have left the mesial plate. In these, therefore,
the basal portions of adjoining zocecia are in contact, and in that respect the same
as in Rhinidictya. To what extent this fact depreciates the value of the character
of the partial separation mentioned in the preceding paragraph, I am not prepared
to say. Perhaps it finds an explanation in this that the character, or rather the
peculiar shape of zocecium to which the early presence of interstitial vesicles is due,
and which is so characteristic of Devonian and Carboniferous bifoliate Bryozoa, had
not in those earlier times become fully established.

A remarkable agreement of structure is presented by certain forms of Pachydic-
tya (Section a) with the Carboniferous fistuliporoid genus Meekopora ce. g. M. clausa
Ulrich). That there exists real or ancestral affinity between them I doubt, yet, if
there is none, the similarity between them is all the more curious. Nor does it seem
likely that the relations with the Cystodictyonide are any closer. Still, it cannot be
denied that the evidence at hand points to a relationship with those families on the
one side and the Rhinidictyonide on the other.*

*A point of general interest presents itself here. As is well known, Nicholson and perhaps the majority of European
paleontologists regard Fistulipora and its allies as belonging to the Alcyonaria group of corals. Now, if we will take the
various species of Pachydictya, starting with the small forms comprised in Section b, which everyone concedes to be
unequivocal Bryozoa, and going through to such forms of Section a us have the vesicular interstitial tissue well devel-
oped, we establish a chain of evidence tending very strongly to prove their view wrong. The lunarium only is lacking
to make the chain complete, but, us is well known, that feature is not restricted to the Fistuliporidw. Indeed, it is as
well, if not better, developed in such universally conceded Bryozoa as the Cystodictyonidw and Ceramoporidw. But this
is onlylone of many chains that I would very willingly publish if it were not for the time consumed in writing them up,
BRYOZOA. 149
Pachydictya.]

Section a: Species in which the zoarium is not limited, and macule or clusters of
_ large zowcia are present.

Pacuypiotya FoLIATA Ulrich.
PLATE IX, FIGS. 1-5; PLATE X, FIGS. 5-10.

-Pachydictya foliata ULRicH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 73.

Zoarium growing from an attached basal expansion into erect, thin fronds,
undulating and simple, or dividing palmately or irregularly ; both sides cellulife-
rous; attaining a hight and width of 50 mm. or more, but specimens larger than 25
mm. square are rare; usual thickness about 1.2 mm., but in some old examples it is
quite 3.0mm. Margin of fronds acute or rounded, often with a distinct non-periferous
border. At intervals of 3.5 or 4.0 mm. the surface presents solid, substellate spots or
macule, that in-most cases are on a level with the general plane of the surface, in
others occupying the summits of low monticules, while in rare instances they may
be even slightly depressed. These macule usually appear smooth, but when well
preserved are seen to be finely grano-striate. Zocecial apertures large, oval, arranged
in regular diagonally intersecting series, in which fourteen or fifteen of the average
size is the usual number in 5 mm. In the immediate vicinity of the macule they
are larger, attaining a size of 0.4 mm. by 0.8 mm., the average size in the spaces
between the macule being about 0.3 mm. by 0.2mm. There is a slight difference
also in the size of the apertures of the old and young specimens, they being largest
in the latter. Interspaces usually of less width than the zoccial apertures, concave
and forming a distinct peristome around the aperture in the young examples ; becom-
ing flattened and even faintly convex, also minutely granulose with age. Interstitial
vesicles seen at the surface in the youngest specimens only.

In vertical sections the zocecial tubes arise rather abruptly from the mesial lam-
ine, the course to the surface throughout being also unusually direct. The prostrate
or primitive-cells may be in contact, with a thin divisional wall; but this is not the
rule since the interstitial vesicules are developed at the same time. The character
of the latter is clearly preserved for a distance of about 0.5 mm. on each side of the
mesial lamine, but beyond this they are filled with solid material in which they are
butilly traceable. Occasionally it is possible to detect faint dark lines passing vertically
through this solid filling, indicating that communication was maintained with the
horizontal median tubuli. The zocecial tubes are bordered on each side by a double
line, and crossed, according to age, by from one to five complete diaphragms. These
occur approximately on the same level in all the tubes, and at intervals correspond-
ing more or less nearly with the diameter of the tube. If my view is correct, each
150 THE PALEONTOLOGY OF MINNESOTA
[Pachydictya.

of these diaphragms represents the floor of distinct zocecia which have succeeded
each other by direct sequence, the formation eventually of the present “tube ” being
the necessary result.

In tangential sections, obtained by grinding down into one of the fi of the
zoarium, we notice characters as follows: Beginning with the base of the zocecia,
i.e, the mesial laminz, we find them represented by a darkened space, (usually a
meandering streak across the deepest part of the section) crossed by two sets of
parallel lines, one, colorless, representing the “median tubuli” that are inclosed
between the two halves of the basal plate, the other, of a dark tint, the longi-
tudinally directed side walls of the zocecia and intertstitial vesicles. Imme-
diately above this space the zocecia are slightly elongate, with the anterior end
widest and rounded, and the posterior end usually truncated. Behind this is a
darkened narrow space which, though really an interstitial vesicle, often appears to
be a part of the zocecium. The two together are somewhat bottle-shaped. Directly
following this stage the zocecia become shorter, broadly elliptical in shape, and sepa-
rated from each other by narrow interspaces in which the elongated interstitial
vesicles are more or less plainly visible. In the next stage the vesicles are more
and more obscured by a seemingly structureless deposit of sclerenchyma, while the
bounding wall of the zocecia becomes more ring-like. If the section is a good one
and the preservation favorable, this wall will be seen to consist of a closely arranged

row of minute tubes, apparently of the same nature as the minute tubuli between
the mesial lamin. In the last stage observed (seen in a section showing the struc-
ture just beneath the surface of an old example) the interspaces are traversed by
one or two intertwining lines of minute dark spots (median tubuli) and a ring of
sclerenchyma, of light color and laminated structure, deposited on the inner side of
the zocecial wall.’ The macule, consisting of aggregations of interstitial vesicles, go
through the same changes as the ordinary interspaces.

Good transverse sections dividing the zoarium vertically, but at right angles to
the direction of growth, show, among other features, the minute tubuli between the
mesial lamine in a very satisfactory manner. A significant fact is that one of these
tubuli seems always to be placed immediately beneath the walls of both the zocecia
and the intercalated vesicles. This is true, 1 believe, of all the Rhinidictyonide, and
is strong evidence in favor of my view that the two sets of minute tubuli, horizontal
and vertical, prevailing in this family of Bryozoa, communicated with each other.

A very similar form occurs near the river level at Ottawa, Canada, but as it pre-
sents several internal peculiarities, especially in the form and arrangement of the
primitive portion of the zocecia, I will pass it by with this mere mention. |
BRYOZOA. 151
Pachydictya.]

The foliaceous zoarium of this species will distinguish it from all associated
Bryozoa excepting Stictoporella Srondifera, Both occur commonly on the same slabs,
and a careless collector might confound them. Still, after a little study, the differ-
ence in the size and shape of their respective zocecial apertures will become so evi-
dent. that they may be distinguished at a glance. .

Formation and locality—Restricted to and very characteristic of the the lower third of the Trenton
shales. It is very abundant at Minneapolis and St. Paul, and has been found in greater or less abundance

marking this horizon in the shales at localities near Cannon Falls, Preston, Fountain and other points in
Minnesota. -

Mus. Reg. No. 5948.

' Pacuyprcrya ocoipentaLis Ulrich.
PLATE VIII, FIGS. 20-27; PLATE IX, FIGS. 6-10.

Pachydictya occidentalis ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 75.

Zoarium variable, sometimes consisting of narrow branches with subparallel
margins, in other cases spreading rapidly into slightly undulating fronds ; but the
commonest mode of growth is represented in figures 20 and 24 on plate VIII. In
these we have wide branches, with more or less divaricating margins, often of sub-
palmate form, with three or more small divisions above. Width 4 to 25 mm.,
greatest thickness 1 to 2mm. Margins acute, usually with a narrow, smooth or
finely striated border, best developed in the narrowest examples. The wider
specimens generally with only a single row of small solid spots having the same
structure as the non-poriferous border. These vary considerably in size, and are not
uniform even on the same specimen. In the narrow examples they are absent
except one or two just beneath each bifurcation. Zocecial apertures elliptical,
arranged in comparatively irregular series, the longitudinal predominating. Curved,
transverse, and diagonally intersecting rows are also to be made out. Measuring
lengthwise, thirteen or fourteen in 5 mm.; transversely, seven or eight in 2 mm.
Interspaces generally rather narrow, but unequal. When an alternating arrange-
ment of the zowcial apertures prevails, the end spaces are decidedly the narrowest,
averaging in that case only about 0.1 mm., or scarcely more than half the width of
the lateral spaces. When however a transverse arrangement obtains they are
nearly equal at 0.13 mm. As a rule we may say that the shorter or transverse
diameter of the zoccial apertures is about equal to the width of the interspaces.
Generally the interspaces are to be described as flattened, finely grano-striate, the
striee, however, appearing to be irregular or interrupted at short intervals. In old
examples they may be convex, but in no case have I detected longitudinal ridges
between the rows of cells. Figure 26 represents one of a number of specimens, the
growth of which for some unknown reason has not been regular and continuous
152 THE PALEONTOLOGY OF MINNESOTA. Lapin Hts
{Pachydictyi.

over the whole surface. There seems to have been a cessation of developement in
~ some places, causing the formation of irregular furrows, in which the old zocecial
apertures are partly closed by a sheet of dense material. Thin sections failed to reveal
anything unusual, hence, we may safely assume that these specimens present merely
an abnormal condition of the species.

Of internal peculiarities brought out by tangential sections the most striking
are, (1) the unusual brevity of the end spaces. In many cases these are so short that
the outer lines of the ring-like walls of succeeding zocecia are often nearly in con-
tact. Generally the length of these spaces is less or about equals half the transverse
diameter of the zovecia ; (2) the continuous longitudinal lines of median pores (there
is as a rule only one in each interspace between the rows of zocecia) appears more
flexuous than usual; and (3) the maculz or solid spots, which do not interrupt the
course of the lines of median tubuli. A number of isolated tubuli, otherwise seem-
ingly of the same nature, occur between the lines mentioned. °

In vertical sections the zocecial tubes frequently have diaphragms, their course
to the surface is less direct than common, and the interspaces or walls unusually
thin.

The growth and maculose surface distinguishes this species from the other Min-
nesota forms of the genus, none of which are found, however, in the same beds with
P. occidentalis. Though perhaps still to be regarded as intermediate in some respects
between P. acuta Hall, sp.,and P. fenestelliformis Nicholson, sp., further investigation
proves the relatiouship to those species to be more remote than I thought at first.
It seems also to have preceded both in time. Compared with the first it is found to
differ in its mode of growth, the zoarium: being wider, in the character of the inter-
spaces, and in the macule which are wanting in that species. The second has larger
zocecia, and both present well marked internal differences.”

Formation and locality—Rather abundant in the upper third of the Trenton shales at St. Paul,
Minnesota. A few specimens also from the same horizon in Goodhue county.

Mus. Reg. Nos. 5949, 7646.

~

Section b: Species in which the width of the zoarium is limited, and the margins
subparallel.

PacHyDIcTYA FIMBRIATA Ulrich.

ee
®

PLATE VIII, FIGS. 28-34; PLATE IX, FIGS. 13 and 14.
Pachydictya fimbriata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 75.
Zoarium rather small, ramose, the branches with subparallel margins, from 2 to

5 mm. wide, averaging a little over 3 mm., thin, the thickness rarely exceeding 0.5
mm.; bifurcations dichotomous, occuring at variable though generally at long inter-
Pachydictya,] BRYOZOA. Ihe
vals; angle of bifurcation unusually wide. Non-poriferous margin very wide,
extremely thin and sharp, and wavy or ruffled; its surface is obliquely striated,
the striz really rows of minute hollow papilla, which communicate with the hori-
zontal median tubuli between the mesial laminz. Zocecia in from seven to twelve
ranges, the usual number ten or eleven; their apertures elliptical, usually a little
wider than the transverse interspaces, and longer than the end spaces. In the five,
six, or seven central rows the apertures are arranged in regular alternating or sub-
alternating longitudinal series, in which thirteen or fourteen occur in 5 mm.; meas-
uring transversely six rows take up a space of 1.5mm. wide. The one to three
marginal rows are not so regular in their arrangement, they being, besides, appre-
ciably larger and separated by wider interspaces, while their long diameter is, usually
at least, directed somewhat obliquely outward.

On plate IX, fig. 13 represents part of a tangential section, showing, at the top,
the primitive or prostrate portion of the zocecia, and mesial laminz with horizontal
tubuli: along the right side, the wide non-celluliferous border, which in thin sections
is irregularly outlined and incomplete, because of its “ruffled” character ; and in the
lower left-hand fourth, the zocecia and interspaces as they appear just beneath the
surface. In the last portion of the figure the chief feature to be pointed out is the
unusual clearness and thickness of the ring-like zocecial investment. Incommon with
perhaps every species of this section of the genus, and many of section a, the longi-
tudinal arrangement of the zocecia between distinct lines, either straight or flexu-
ous, and proving on closer inspection to be series of minute pores, prevails in the
central rows through all stages, saving, perhaps, the last in very old examples.

Good examples of this species cannot be confounded with any other known to
me, since the great width and wavy or ruffled character of the non-poriferous
margin gives them a very striking and highly characteristic aspect. In most other
respects the species resembles P. acuta Hall, sp., and its western varieties rather
closely. It may be compared also with P. elegans and its described variety. In that
species and variety the non-poriferous margin is also rather wide, but it is not wavy
and the inter-apertural spaces are wider, especially those between the ends of the
zocecial apertures, while the whole surface of the zoarium strikes one as more highly
ornamental. Considerable differences are likewise to be noted in tangential sections
as may be seen in comparing figuies 8 and 13 on plate IX.

Formation and locality.—Rather common in the lower half of the Trenton shales at Minneapolis and
St. Paul, Minnesota. It occurs also in the “Pierce” limestone of Tennessee.

Mus. Reg. Nos. 5950, 5951.
154 THE PALEONTOLOGY OF MINNESOTA.
[Pachydictya.

PACHYDICTYA ELEGANS. ”. sp.

‘PLATE VIII, FIGS. 18 and 19, PLATE IX, FIGS, 8 and 9.

The nearly complete type specimen began its growth on the extremity of some
undetermined ramose bryozoan. The basal expansion is small, and its surface
largely covered with granulose striz. At its edges, where it grew downward on the
foreign body, a few apparently normal zocecia were developed. From the exceed-
ingly short, neck-like constriction above the base, the erect portion of the zoarium
divides at once into three branches, and two of these continue to divide dichoto-
mously with extraordinary frequency, the average distance between bifurcations
being only 50r6mm. This frequent division caused the zoarium to spread with
unusual rapidity ; some of the inner branches must have overlapped if continued.
We may assume, however, that with age, beyond that shown in this example, the
outer or subsequent divisions became less frequent, or at any rate, dependent upon
the space available for lateral development. Branches 2.5 mm. to 5.0 mm. wide,
thin, edges sharp, non-poriferous, border wide, obliquely grano-striate. In the
thickest specimens the celluliferous portion of the branch rises abruptly from the
wide non-poriferous borders, the growth of the latter having failed to keep pace
with that of the zocecia. Under a good hand lens the surface presents a highly
ornamental appearance, the arrangement of the zoccia and sculpture of the
interspaces being very regular. Apertures elliptical, separated from each other
by spaces as wide as their shorter or transverse diameter. In the central rows
the arrangement is alternate, with thirteen or fourteen in 5 mm., measuring
lengthwise, and seven of the central rows in 2 mm., transversely. Those in the
marginal rows slightly oblique, a little larger than the average and separated
by correspondingly wider interspaces, so that a smaller number occurs here in a
given space than in the central series. Surrounding each aperture a sharply defined
rim or peristome, and rising from the center of the depressed spaces between the
longitudinal rows, a faintly flexuous, thread-like line. On the best preserved por-
tions of the surface, both the longitudinal lines and the peristomes are seen to carry
a row of minute papilla. Over the central part of the surface the depressed end
spaces are narrow and usually empty, but toward the margins, where they are
wider, they are occupied by a gradually increasing uumber of papille, at first
isolated, then forming short outwardly tending rows.

Provisionally I propose to place here a number of specimens agreeing in all
respects with the type ofthe species, save in this, that they bifurcate at less frequent.
intervals. The interspaces in many are a trifle thicker, but as these specimens are
heavier and evidently older, that is to be expected.
BRYOZOA. 155
Pachydictya.]

The internal characters, which in most respects remind us greatly of P. occident-
alis, surely more of that species than of P. acuta, were obtained from thin sections
of one of the last mentioned specimens.

Compared with other species P. occidentalis offers many points of agreement,
but, so far as known, is distinguished readily enough by its macule, and the less
regular arrangement of its zocecia and inter-apertural markings. P. fimbriata is
also closely related, but the peculiar wavy character of its borders serves well in
separating them.' In P. acuta and varieties the spaces separating the rows of
apertures are more ridge-like, and the end spaces longer. The branches also are,
except in rare instances, narfower.*

Formation and locality—Not uncommon in the Galena shales at St. Paul, Minnesota, where it is
associated with an abundance of Zygospira recurvirostris (Hall) and segments of Arthroclema. Arthropora
reversa is found on the same slabs of rock. Also at Decorah, Iowa.

Mus. Reg. No. 7596.

Pacuypictya acura Hall, and varieties.

PLATE VIII, FIGS. 11-17; PLATE IX, FIG. 7.

Stictopora (?) acuta HALL, 1847. Pal. N. Y., vol. i, p. 74, pl. xxvi, figs. 3a, b.

Stictopora or Ptilodictya acuta (part.) of many authors.

Stictopora acuta ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 168, pl. viii, figs. 1, la, 1b.

Pachydictya acuta ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat Hist. Sur. Minn., pp. 75 and 76.
: (Merely mentioned as a species of Pachydictya.) :

This so frequently yet so often incorrectly quoted species, has given me no little
trouble, first, because of the difficulty of determining exactly what species Hall
originally intended, and second, because of its variability. The species might be
subdivided, but I doubt the advisability of doing so, since most of the varieties are
exceedingly difficult to recognize. The species, with all its varieties, is also restricted
to the Trenton limestone, or rocks equivalent to that horizon. Hence, we have not
the usual though good excuse for proposing varietal distinctions. The species is to
be regarded as one of the most characteristic and widely distributed fossils of the
Trenton proper, being also abundant at many localities in New York, Vermont,
Canada, Kentucky, Tennessee, Illinois, Wisconsin, Minnesota, and Manitoba. It has
been reported to occur in the Birdseye and Black River horizons, but that is most
likely an error, species of Rhinidictya, which abound in those rocks, having but too
often been confounded with P. acuta.

Figure 11 of Plate VIII, represents one of seven fragments from the original
locality, Trenton Falls, New York, which I owe to the kindness of 3.r.C. D. Walcott.
Its surface magnified nine diameters is shown in fig. 12 of the same plate. In this

* Though now obliged to regard P, elegans as specifically distinct, I expect, with material soon to be gathered, to be able
to show that it is merely a later development of P. occidentalis, Perhaps also that it is really an intermediate stage between

that species and P. acuta.
156 THE PALEONTOLOGY OF MINNESOTA.
. (Pachydctya.

specimen, which may be assumed to represent the typical form of the species, the
zocecial apertures are elliptical, rather small in the central rows where, however,
they are separated by comparatively long intervals, with twelve in5 mm. In the
marginal row the zowcial apertures are rather oblique and conspicuously larger,
and here only eight or nine are to be counted in the same space. The non-porifer-
ous margins are wide, and where the preservation is good, have the usual oblique
granulose striation. The interspaces form faint longitudinal ridges, while a delicate
rim is to be detected here and there around the sunken apertures. In some of the
other fragments the surface is preserved better, or, as is more likely, it presents a
less aged condition, and in these the peristome is more distinct, as is also a thin
raised line passing between the central longitudinal rows of apertures. The general
effect, therefore, is much as in fig. 32 of the same plate, only the zocecial apertures
are narrower and farther apart, and the marginal ones larger.

The New York, Canadian and Vermont’ specimens, or as we may call them, the
eastern form of the species, is fairly constant in every respect. The zoarium divides
dichotomously at rather long intervals, the length of these varying between the
extremes of 10 and 20 mm., while the width of the branches between the bifurcations,
where the margins are parallel, is rarely more than 3.0 mm., and so far as noticed,
never less than 2.6 mm. .The number of rows of zoccia is generally seven or eight,

In the western form, however, we find a greater or less degree of instability in
nearly every character. This is to be remarked especially of the Minnesota speci-
mens. The branches, as a rule, are considerably wider, the average varying between
3.5 mm.and 5.5mm. Still, it is not rare to find specimens, particularly among those
from the lower beds of the Galena limestone, that are narrower, with the average at
about 2.0mm. Figure 16 represents an example that may be compared with the
eastern form in the matter of branching, but in a great majority of the western
specimens the divisions are much closer, the average distance between them being
about 10 mm., and in many less. Another point to be noted is the tendency to
irregularity in the growth of the zoarium of the western form, abortive branches,
trifurcations and unparallel margins being common, while its appearance in general
“is less rigid than is prevailingly the case in the eastern form. The non-poriferous
margin may be wide or narrow, but it is rare, if it ever occurs, to find an amount of
difference in the size of the zocecial apertures in the marginal and central rows
equalling that prevailing in the eastern form. As a rule, the difference may be
stated to be greatest in the smaller examples and least in the wide ones. The num-
ber of zocecia rows varies from six to eighteen, with eleven, twelve and thirteen the
number most frequently met with. In the central rows twelve, thirteen or fourteen
apertures, the two last numbers more common than the first, occur in 5 mm. In
Pachydictya.] BRYOZOA. 157

well preserved examples a thin peristome is clearly distinguishable, and, running
lengthwise between the rows of apertures, a thin ridge raised considerably or only
slightly above the level of the peristomes. The interspaces are always’as wide as
the zocecial apertures, and in many specimens nearly twice as wide. One specimen
preserves a few “closures” or zocecial covers. These are faintly convex, with a small
rounded opening in the anterior half. @

Of internal characters, I shall mention, (1) the absence of interstitial vesicles
between the primitive or prostrate cells of the zocecia ; (2) the contact of those por-
tions of the zocecia with each other on all sides, resulting from the absence of the
vesicles ; (8) the peculiar convex shape of the anterior or transverse partitions of the
primitive cells; (4) the density and early beginning of the solid interstitial filling,
and consequent indistinctness of the vesicles. Diaphragms are usually present, one
or two in each tube.

Compared with other species, P. elegans is found to differ, externally, in its usu-
ally wider and more rapidly branching zoarium, and flatter interspaces ; internally
in the shape of the primitive cell and the earlier development of the intersititial
vesicles. P. occidentalis is sufficiently distinguished by its mode of growth and its
maculose surface, and P. fimbriata by its peculiar ruffled non-poriferous margin.

Formation and locality.—This species is one of the commonest fossils of the Galena shales, having
been found at perhaps every one of the numerous localities in the state where that horizon is exposed.
Also at Decorah, Iowa. It occurs also in the lower layers of the overlying limestones, at Fountain, and
several specimens have been collected from the Phylloporina corticosa horizon. Its wide geographical dis-
tribution outside of the state has been mentioned already.

Mus. Reg. Nos. 7607, 7609, 7616, 7619, 7623, 7632, 7639, 7643, 8027.

Pacnypiotya pumILA Ulrich.
PLATE X, FIGS. 1-4.

Pachydictya pumila ULnicu. 1890. Jour, Cin. Soc. Nat. Hist., vol. xii, p. 186, fig. 11.
Rhinidictya humilis ULRicu, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 185, fig. 10.

Zoarium bifoliate, small, usually less than 1 cm. in height, growing rather
irregularly. Branches from 1.0 to 1.5 mm., wide, generally bifurcating at intervals
of from 2 to 4mm., but some fragments observed are undivided for a distance of 6
or8mm. Zocecia in from three to six ranges, with four or five the average number
shortly after bifurcations. The arrangement of their oval apertures is inclined to
be rather irregular, though more or less longitudinal rows prevail in most cases.
Over the basal parts of the zoarium this irregularity is apparent in a higher degree
than in the distal portions. In the latter five to seven occur in 2 mm. longitu-
dinally. The size of the apertures and the general appearance of the surface varies
with age and other conditions, Nearly complete examples may show all the phases,
158 THE PALEONTOLOGY OF MINNESOTA.
[Pachydictya.

In the very young specimens, or at the distal extremities of the branches of the
more mature ones, the zoccial apertures are comparatively large, the lateral inter-
spaces correspondingly narrow, and the end spaces with one or two depressions. In
this stage the interspace granulations are very faint, but in the succeeding stages they
are much better defined, the apertures often smaller, with the width of the inter-
spaces increasing with greater rapidity, the increase in the circumference of the
branches being divided between the lateral interspaces. In most of these specimens
the interspaces are now flat or faintly concave, with a more or less distinctly recog-
nizable though thin peristome about the apertures. In others a row of the inter-
stitial papille occupies a faint longitudinal ridge, that may be elevated to slightly
above the level of the peristomes. In more rare instances the peristomes appear to
be wanting over parts of the surface, and the whole interspace convex and irregularly
granulose, and seeming to slope down into the apertures. These specimens have
quite a different aspect from the ordinary form of the species, indeed, so much so, that
I mistook them for a species of Rhinidictya. Non-poriferous margin never wide,
often so narrow as to be practically wanting. Its surface is papillose. Not infre-
quently large patches of the surface, where the zocecial apertures have been closed
by a thin deposit of calcareous material, are covered with such papille.

Internal characters vary much as in P. acuta, excepting that they are all a little
smaller, and the transverse walls between the prostrate.cells of the zoccial tubes
straighter.

. When the preliminary description of this species was written I had unfortunately
mislaid the two specimens regarded as the types of the form named Rhinidictya
humilis, and which I believed to have been derived from the lowest shales at Minne-
apolis. In preparing the Minnesota materia] for my final studies they were found
and the label with them proves that they were really collected at the same time and
from the same beds as the original specimens of P. pumila. Later washings of the
shales from this locality have added greatly to the number of specimens. With
this more complete representation of the species I have become satisfied that the
supposed Rhinzdictya exhibits merely another phase of surface marking of P. pumila,
deserving not even subordinate distinction. Among the lot, however, there is a form
of which I[ have over twenty specimens, that might be distinguished as var. sublata.
The zoarium does not appear to have been much larger than in the typical form, but
its branches are wider, and though there are generally two or three rows of zoccia
more than in the largest of the type form, the greater width of the branches is
chiefly due to a wide non-poriferous margin.
Pachydictya.] _ BRYOZOA. 159

The small, dwarfish appearance of the zoarium of this species will distinguish it
from all others of the genus known to me. In other respects the species resembles
P. acuta Hall, which occurs associated with it, but because of the much smaller size
of P. pumila confusion between them is rendered highly improbable. Another asso-
ciated species, Ehinidictya minima, is more likely to be confused with it, but after a
little comparative study, the student will find himself able to distinguish them
almost at a glance.. The rather rigid and subcylindrical character of the stems of
the next described P. triserialis are sufficiently distinctive of that species, and render
further comparisons unnecessary.

Formation and locality.—Base of the Galena shales, near Cannon Falls, Minnesota, where it is asso-
ciated with species of Nematopora, Arthroclema armatum, Helopora mucronata, and other small Bryozoa,
all of them characteristic of the horizon. A single example apparently referabie to this species, was found
at the horizon of Phylloporina corticosa, and another occurs on a slab of Trenton limestone, from Trenton
Falls, New York.

Mus. Reg. No. 8107. : °

PacHYDIOTYA TRISERIALIS Ulrich.
PLATE X, FIGS. 11-14.

Pachydictya triserialis ULRicu, 1890. Jour. Cin. Soc, Nat. Hist., vol. xii, p. 187, fig. 12.

Zoarium consisting of very slender, parallel-margined, subcylindrical or com-
pressed branches, 0.6 to 0.8 mm. wide, and 0.3 to 0.55 mm. thick; branches bifurcat-
ing at intervals of from 5 to 10 or more mm., oval or obtusely hexagonal in cross-
section, the margins never, or at any rate but rarely, acute, in most cases to be
described as narrowly rounded. Each face with three rows of longitudinally
arranged zocecial apertures, occasionally with a fourth row, but only for a short
distance. These rows are often not exactly parallel with the margins of the
branches, a faint tendency to arrangement in long spirals being perceptible in
those cases. Zocecial apertures elliptical, nearly twice as long as wide, largest in
young or worn examples, separated by intervals equal to their long diameter, with
from 11 to 13 in 5 mm.;. occasionally enclosed by a delicate rim or peristome, but
oftener with sloping edges. Between the rows an obtuse ridge. Entire surface,
especially of the older portions, minutely papillose. Non-poriferous margins nar-
row, readily overlooked, generally wider on one side than on the other.

Internal characters similar to those of P. acuta Hall, and P. pumila. In sucha
small species the interstitial vesicles are necessarily reduced to a minimum, and
in this one the solid filling of the interspaces is so dense that their original presence
is not easy of demonstration.

The subhexagonal narrow branches of this species present considerable resem-
blance to species of Nematopora like N. lineata (Helopora Billings). Of course, there
160 THE PALEONTOLOGY OF MINNESOTA.
: [Trigonodictya.

is no real affinity between them, this being, as is clearly shown by transverse sec-
tions, a bifoliate zoarium, while in Nematopora the ‘zocecia diverge equally in all
directions from the center of the branch. Iam not acquainted with any species of
Pachydictya, nor with any associated species of bryozoan, with which the slender
ramulets of P. triserialis might be confounded.

Formation and locality.—As yet known only from the Trenton limestone at Montreal, Canada, but
it is not at all unlikely that the species is to be found in the Minnesota equivalent, of that horizon.

Genus TRIGONODICTYA, n. gen.

Zoaria with triangular branches, constructed upon the plan of Prismopora, but
with zocecia and all minute details of structure precisely as in Pachydictya.

Type: Pachydictya conciliatrix Ulrich.

Another species occurs in the Clinton rocks near Eaton, Ohio, which, because it
is the only bryozoan with triangular branches known to me from Upper Silurian
strata, and may therefore be distinguished from associated forms with ease, I pro-
pose to name Trigonodictya eatonensis,n.sp. It is rather more slender than the Trep-
ton species, and its branches divide at less frequent intervals. The three surfaces
are also flat instead of concave, while in thin sections the interspaces between the
comparatively large oval zocecia are thinner, and the lines of erect median tubuli

much less distinct and not so numerous.

TRIGONODICTYA CONCILIATRIX Ulrich.
PLATE IX, FIGS. 11 and 12; PLATE X, FIGS. 15-20.

Pachydictya conciliatrix ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 76.

Zoarium of irregular growth, dividing at frequent intervals, consisting of equal-
sided triangular branches, with the three faces concave, each averaging about 3 mm.
wide; or of more or less rapidly spreading, small, flabellate fronds, with from one to
five salient, divaricating ridges on only one or both sides. All intermediate condi-
tions between these two extremes occur. Kach of the surface ridges has a non-
poriferous, sharp summit, and, beginning as a mere line, it rises gradually until it is
sufficiently high to permit of the formation of a new triangular branch, when it
forms one of its edges. Zocecial apertures elliptical, slightly oblique, smallest and
arranged longitudinally over the central half of each face; here with 12 or 13 in 5
mm.,, a faintly elevated line between the rows, and the width of the longitudinal and
lateral interspaces generally about equal to the respective diameters of the aper-
tures. Toward the non-poriferous edges the apertures are directed obliquely upward
and outward, and increase in size gradually till those in the outermost row are quite
Trigonodictya, BRYOZOA. 16 1

twice as large as those in the central rows. When the surface is weathered the
zocecial apertures are larger than normal, and their longitudinal arrangement less
obvious, the interspaces rounded, and without the series of minute papille that are
always present when the surface is well preserved.

In considering the internal characters it should be borne in mind that but few
tangential sections are at all likely to be made that will show the structure as fully
and clearly as in fig. 12 (plate IX). The section from which this drawing was made
is an exceptionally good one, having been prepared from a fragment in an unusually
good state of preservation; so that it shows the structure just beneath the surface in
a very satisfactory manner. At the sides of the figure, the left-hand one especially,
the horizontal median tubuli are represented, and a short distance from the edge we
see how the vertical series of these tubuli arise out of the horizontal set.* At
a deeper level than any shown in the figure, the zocecia are larger and rounder, and
the interspaces proportionally narrower, and, with the exception of a dark line run-
ning longitudinally between the rows of zocecia, generally appear structureless. A
little deeper and a few irregular lines, representing the walls of interstitial vesicles,
may be noted in the interspaces.

Transverse sections show that in the regularly developed triangular branches
each is divisible into three subequal triangular parts, bounded by a mesial line from
which the zocecial tubes of each part proceed to their respective external faces.
New angles and faces are produced by raising one of the plate-like longitudinal
walls until it has assumed the characters of a mesial plate.

The zoarial features of this species are so strikingly different from all known
Lower Silurian Bryozoa that comparisons are unnecessary. For remarks on the
Clinton group species of the genus, see under the generic description.

Formation and locality.—A pparently restricted to the upper third (Phylloporina horizon) of the
Trenton shales, near Cannon Falls, Minnesota.

Mus, Reg. No. 5952.

Family PTILODICTYONIDA, Zittel.

For a description and remarks on this important family, the reader is referred
to my recent work in the eighth volume of the reports of the geological survey of
Illinois, pp. 348 and. 390.

Five genera of this family are represented in the Trenton shales of Minnesota,
and, so far as known, the species here described of each are the earliest existences

 

*This is not only an interesting fact, but, as are all that relate to the intercommunication of the zooids, also one of

great importance morphologically.
—11
162 THE PALEONTOLOGY OF MINNESOTA.
" LPtilodictyoni dz.

of not only their respective genera but of their entire family. In every case the
generic features are fairly developed, indicating that the primal stock is yet to be
discovered in previously deposited rocks. Still, in the three most typical members
of the family, Ptilodictya, Escharopora and Phenopora, the resemblance between the
primitive species of each is more evident than in the species that occur in deposits
of later date.

Indeed, in these early Bryozoa we often meet with species that combine, some-
times to a very perplexing degree, characters which in latter times have attained
the stability and importance of generic structures. Escharopora confluens and E. (?)
limitaris are cases in point, since they have much to remind us of Phenopora; not of
the fully differentiated Upper Silurian forms of that genus, but of the Lower Silurian
species which obviously had not yet attained the full expression of the generic char-
acters. From the facts already available we are, I believe, justified in assuming either
that Ptenopora and Escharopora are contemporaneous offshoots from a more primi-
tive stock, with characters in general like those of E. confluens; or that Escharopora
was the stock from which first Phenopora and then Ptilodictya were evolved. In the
development of the former, the connecting channel between the apertures was cut
off by the formation of a rim at their ends. The mere depression to which the chan-
- nel was thereby reduced, was next deepened, chiefly at the ends, thus giving rise to
the two mesopores between the ends of the zocecial apertures. These are already
well developed in Phenopora incipiens, but like all incipent characters are as yet a
little unstable. The later development of the genus consisted principally in the
greater separation of the longitudinal walls between which the primitive cells were
arranged. This caused a shortening of the longitudinal inter-apertural spaces, with.
the result that the “two mesopores” were obliged to change their arrangement from
the longitudinal to the transverse.

The prostrate portion of the zocecial tubes of early Phenopora is very narrow
and elongate, just as in the contemporaneous species of Escharopora, and the ten-
dency to shorten and widen the primitive cell (already mentioned) exhibited in
Middle and Upper Silurian times, seems to have obtained through all the most
typical members of the family. .

The systematic position of Stictoporella is undoubtedly near that of Intrapora,
Hall, Teeniodictya, Stictotrypa, and Ptilotrypa, Ulrich. These five genera, it seems to
me now, should be classed together, but whether they ought to be regarded as con
stituting a distinct family by themselves, or had best be retained as members of the
Ptilodictyonide, the position assigned to them in my recent work on the Illinois
Bryozoa, is a question that I am not yet prepared to solve. The Ptilodictyonide
would surely be a more compact and obviously characterized group if they were re-
Ptilodictya.] BRYOZOA. 163

moved, for in that case we would have one easily recognized though not peculiar
character running through the tamily that is not represented in Stictoporella and
allied genera.* A basal articulation, namely, pertains to Ptilodictya, Escharopora,
Phenopora, Clathropora, Graptodictya, and Arthropora, while in Stictoporella and
genera of that type, the zoarium is continuous throughout, and attached below in
the ordinary manner, 7.e. by a simple basal expansion forming one piece with the
erect frond.

If removed from the Ptilodictyonide it would be necessary to establish a new family
for their reception, since they cannot, because of the absence of median tubuli
between their mesial lamin, be placed with the Rhinidictyonide, the only remain-
ing family of paleozoic Bryozoa with which they have any affinity. It was because
they agree in this and most other respects with Escharopora, that I arranged them
with the more typical Pétilodictyonide. The new family would hold an intermediate
position between the Rhinidictyonide and Ptilodictyonida, differing from the former
in its zocecial characters, and from the latter in its continuous zoarium, presumably
a zoarial modification.+

Genus PTILODICTYA, Lonsdale.

Flustra (part.), GOLDFuss, 1826. Petref. Germ.

Ptilodictya, LONSDALE, 1889, Murch. Sil. Syst., p. 676.

Ptilodictya (part.), NICHOLSON, 1874. Geol. Mag., n.s., vol. i, p. 123, and Pal. Ont., p. 97; VINE, 1881
Second Brit. Assoc. -Rep. Foss. Poly., Quar. Jour. Geol. Soc. Feb. 1882,
and 1884, Fourth Brit. Assoc. Rep. Foss. Pol., p. 37; Uuricu, 1882,
Jour. Cin. Soc. Nat. Hist., vol. v, p. 151, and 1890, Geol. Surv. Ill.,
vol. viii, p. 390; HALL, 1887, Pal. N. Y., vol. vi, p. 19.

Escharopora, HALL, 1874 and 1879. Twenty-sixth and Thirty-second Rep. N. Y. State Mus. Nat.
Hist. (Not 1847, Pal. N. Y.; vol. i.)

Heterdictya, NICHOLSON, 1875. Geol. Mag., and Pal. Ont., (ii) p. 79.

In my preliminary report on the Bryozoa of Minnesota (Fourteenth Ann. Rep.
Geol. Nat. Hist. Surv. Minn., p, 64; 1886) I mention the two sections into which
Ptilodictya, as understood by me in 1882 (loc. cit.), may be divided. Since then I have
given the subject further study, with the result that I now believe they may be dis-

tinguished in a generic sense.

*An articulated zoarium is of rather common occurrence among both the living and extinct Bryozoa. Of Paleozoic
types the Arthrostylid@ and true Ptilodictyonide are the best representatives of this method of growth. It is also character-
istic of Acroyenia, Hall, and Dicranopora, Ulrich.

+In drawing this distinction the systematist is once more called upon to decide between zoarial and zocwcial varia-
tions as furnishing the best and most reliable tests of relationship. The more I study these questions of relationship, the
less ‘practical seems the adoption of strict rules for our guidance in the delimitation of the classificatory sections whereby
we attempt to express our ideas of natural modifications. What may appear as, and probably is, sufficient ground for the
erection of a genus or family in one case, does not necessarily suffice in another. There are so many points to be taken into
account before anything even approximately expressing nature’s handiwork can result. Among them. environment, asso-
ciation, and relative position in the geological scale, are of great importance. The last, if judiciously used, is always an
excellent clue to relationship, and one that has been but too rarely taken into consideration by students of recent zoology.
Volumes are to be written upon these intricate questioas, but I have said enough probably to show that a successful classi-
fication cannot be worked out in a day, nor is any yet drawn up that will] not suffer greater or less modification in time. The
bility of a classification depends not a little upon the collector, since it is his discoveries that build it up or tear it down.

 

sta
164 THE PALEONTOLOGY OF MINNESOTA.
[Pttlodictya.

The divisions are perfectly natural, and each based upon readily detected pecu-
liarities. In the first, including P. lanceolata Goldf., sp., and therefore Ptilodictya in
the strict sense about to be proposed, we have a character that is wanting in the
second: Namely, a variable number of regular longitudinal rows of zocecia running
through the center of the fronds from the pointed articulating base upward. In the
earliest species having this peculiarity, these longitudinal central rows do not always
extend through the frond to its upper extremity, but they are sometimes found to
pass into the diagonal arrangement prevailing over the lateral portions of the surface.
In P. magnifica Miller and Dyer, for instance, the longitudinal rows obtain only in the
middle of the lower half of the full grown zoaria, the diagonal arrangement being
present on all other parts of the surface. td

These central zocecia are oblong-quadrate in shape, narrower than the lateral
ones, and always the first to be developed. In the youngest examples of all the
species they alone occur, and it is only in later stages that the differently arranged
and wider lateral zocecia are developed. It is possible that this condition, which, as
said, is an immature or youthful one in most of the species, may have persisted in
some, and that in these no lateral zocecia were produced. P. gladiola Billings, and
P. flagellum Nicholson, may be said to support this view, only longitudinal zocecia
being as yet known of them. Still, as the evidence is merely negative, and in the
light of facts brought out in a study of complete suites of P. variabilis of the Hudson
River group, I am obliged to regard the matter as doubtful.

Used in this restricted sense Ptilodictya admits of subdivision into two groups,
both obvious enough, but, as they now appear to me, not quite natural. In the
first, with P. lanceolata as the type, we have either nothing but longitudinal rows of
zocecia, or these are flanked on each side by spaces of greater or less width
over which the apertures are arranged in an oblique manner, giving the fronds the
fancied resemblance to a feather that suggested the generic name. The lateral rows

.proceed to the edges of the zoarium without interruption from either groups of
large cells, monticules, or macule.

In the second subdivision, and of this P. magnifica M. & D. may be considered
as typical, the zocecial apertures on the lateral extensions of the zoarium are
arranged in diagonally intersecting series, with clusters of large cells, monticules,
or macule, at regular intervals. The pinnate arrangement of parts prevailing in
the lanceolate subdivision is therefore scarcely recognizable in this, but the presence
of monticules is an even more striking peculiarity.

In the second division, for which I propose to adopt Hall’s name Escharopora,* the

 

* [have some slight doubts respecting the specific characters of H. recta, Hall, the original type of the genus, but none
whatever so far a8 its generic characters are concerned. ss saa pee
Ptilodictya.| BRYOZOA. 165

‘diagonal arrangenient of the zocecia prevails throughout ; so that instead of narrow
oblong-quadrate zocecial apertures along the center of the fronds, we have there, the
same as on all other parts of the surface, rounded apertures situated in rhomboidal
or hexagonal spaces. :

. A subdivision of Escharopora is likewise possible, but in this case we make out
three instead of two. In the first we have simple narrow zoaria, with the diagonal
lines of zocecia extending without interruption, completely across the celluliferous
faces. E. recta and Ptilodictya falciformis Nicholson, are good examples. In the
second the zoaria are also simple, but wider, occasionally very large (e. g. Ptilodictya
pavonia d’Orb.) and at regular intervals their surfaces exhibit clusters of large cells.
The latter are commonly elevated into rounded or conical monticules.

These two subdivisions though obvious enough and in the main indicative
of natural relations, are nevertheless not entirely so, since they separate species like
P. falciformis Nicholson, and P. maculata, that most certainly are closely allied, and
in practice sometimes difficult to distinguish even specifically. Again, we know
forms, Escharopora (Ptilodictya) subrecta for instance, in which old examples, or may
be they are entitled to the distinction of a variety, have one, two, or even three rows
of monticules. On the other hand, I am fully convinced that in the young zoaria of
the normally montiferous species, the monticules were, to say the least, a very
inconspicuous feature compared to what they are on the fully matured zoaria
(See footnote, ante p. 146.)

The third subdivision includes the branching forms. So far as known, it isa
natural grouping, and distinguished from the preceding by the branching of the
zoaria, and parallel margins of the branches after the first or basal division. When
the branches are wide, clusters of large cells and monticules are developed, but
when they are narrow, the monticules are absent, and the large cells distributed
along the non-poriferous edges. A subdivision of the branching forms is possible
therefore precisely as in the simple species.

In accordance with the above I offer the following amended definition of Ptilo-
dictya and Escharopora, and classification of species.

Genus PTILODICTYA, Lonsdale, 1839.

Zoaria bifoliate, simple, umbranched, lanceolate or falciform, terminating below
in a solid, striated, pointed base, which originally fitted loosely in the centrally sit-
uated cupshaped depression or socket of a small basal expansion. The latter grew
fast to foreign bodies, is radially striated, and has small cell openings in the furrows
between the stria. In very young examples, and in certain small species in which
166 THE PALEONTOLOGY OF MINNESOTA.
{Ptilodictya.

this condition seems to be permanent, the entire zoarium consists of longitudinally
arranged, narrow, oblong-quadrate zowcia. As growth proceeded new zocecia, both
wider and differently arranged, were added on each side. These lateral zoccia
may be arranged in oblique or transverse rows, so as to produce the “pinnate”’ or
‘““plumose ” arrangement prevailing in the typical species, or they may form diag-
onally intersecting rows, with groups of large cells or subsolid spots raised at
regular intervals into monticules. Zocecial apertures subquadrate, rhomboidal, or
rounded, the shape depending largely on their arrangement.

Both hemisepta usually well developed. Primitive cell, with thin walls, sub-
elongate, quadrangular, hexagonal, or lozenge-shaped, in contact at all sides. In
the vestibular or outer region, the walls are more or less thickened, solid, and with a
double row of exceedingly minute dots ; the latter rarely preserved and seen only in
tangential sections. No median tubuli. —

Type: P. lanceolata Goldfuss, sp.

CLASSIFICATION OF SPECIES.*

Section a; without monticules.

P. lanceolata Goldf., Upper Silurian, Europe.

P. expansa Hall (not Phenopora expansa Hall and Whitefield), Clinton group, Ohio.
P. gigantia (Heterodictya gigantia Nicholson), Corniferous limestone, Canada.

P. canadensis Billings, Hudson River group, Canada.

P. flagellum Nicholson, Cincinnati group, Ohio.

P. giadiola Billings, Hudson River and Anticosti groups, Auticosti.

P.(?) suleata Billings, Anticosti group, Anticosti.

P.?) angusta Hall, Niagara group, Indiana.

Section 6; with monticules.

P. magnifica Miller and Dyer, Cincinnati group, Ohio, Illinois and Indiana.

P. plumaria James (as figured by Ulrich) Cincinnati group, Ohio, Indiana and Illinois. «
P. variabilis Ulrich, Cincinnati group, Ohio and Indiana.

P. whiteavesi Ulrich, Hudson River group, Manitoba.

P. nebulosa Hall, Lower Helderberg group, New York.

No species of Péilodictya, as here restricted and defined, have yet been brought
to my notice from Minnesota deposits, but it is not improbable that P. magnifica
M. and D., occurs in the upper beds of the Hudson River group in the southern part

of the state, that species having been noticed as far to the northwest as Wilmington
and Savannah in Illinois.

* A number of foreign species have been described as Ptilodictya, but in the absence of specimens I do not consider my-
self warranted to attempt their classification,
BRYOZOA. 167

Escharopoa.]

Genus ESCHAROPORA, Hall.

Escharopora, HAL, 1847. Pal. N. Y., vol. i, p. 72.

Ptilodictya (part.), ULRIcH and many other authors.

Zoaria bifoliate, simple or branching, pointed below, and articulating into
a‘spreading base as in Ptilodictya. Zocecia arranged in regular diagonally intersect-
ing series throughout. In the small species these rows extend in a continuous line
across the fronds, but in the larger forms their course is interrupted at more or less
regular intervals by the development of raised clusters of large cells. Apertures
rounded, elliptical or subcircular, set into sloping areas; the latter generally of
rhomboidal or hexagonal shape and sharply defined, in other cases longitudinally
confluent, and connected by a narrow channel.

Internal structure essentially as in Ptilodictya, the differences chiefly due
to the different zocecial arrangements.

Type :.. recta Hall, Pal. N. Y., vol. i, p. 72; 1847.

Better known examples are Ptilodictya falciformis Nicholson, Pal. Ohio, vol. ii, p.
259, 1875, and P. pavonia d’Orbigny, Prodr. de Pal. vol. i, p. 22, 1850.

CLASSIFICATION OF SPECIES.

Section a; zoaria simple, without monticules.

E. acuminata (James), Galena limestone, Iowa; Utica horizon of the Cincinnati group, Ohio and
‘ Kentucky.

E, angularis, n. sp., lower Trenton, Minnesota.

E. falciformis (Nicholson), Cincinnati group, Ohio, Indiana, Kentucky.

E. recta Hall, Trenton limestone, New York, Canada, ? Galena shales, Minnesota.

E. subrecta (Ulrich) lower Trenton shales, Minnesota.

Section b ; zoaria simple, with monticules.

E. hilli (James, as figured by Ulrich), Cincinnati group, Kentucky.
E. libana (Safford), Birdseye limestone, Kentucky, Tennessee.

E. maculata (Ulrich), Cincinnati group, Ohio, Kentucky.

E. pavonia (d’Orbigny), Cincinnati group, Ohio, Indiana, Kentucky.
E.n. sp., Birdseye limestone, Tennessee.

E. n. sp. (near pavonia), top of Trenton, Nashville, Tennessee.

E. n. sp., Cincinnati group, Kentucky.

Section c; zoaria branching.

E. briareus (Ulrich), Birdseye limestone, Tennessee.
E, confluens, n. sp., lower Trenton shales, Minnesota, Tennessee.

E. ramosa (Ulrich), Birdseye limestone, Tennessee, Kentucky.
E. n.sp., Utica horizon of the Cincinnati group, Kentucky.

From the preceding classifications we learn that EHscharopora began in the
“Birdseye” or earlier, and ceased apparently in the age of the Cincinnati group—
strictly speaking, in the middle division of that formation. True Ptilodictya is first
met with in the upper beds of that group of rocks, and continues with varying rep-
resentation up into the Lower Devonian.
168 THE PALEONTOLOGY OF MINNESOTA

{Escharopora.

EScHAROPORA ANGULARIS 2. Sp.

PLATE XII, FIGS. 1-4, 30 and 31.

Zoarium simple, falciform, curved, 10 to 30 mm. or more in length, 2 to 9 mm.
wide; articulating base pointed, with comparatively a small part of the extremity
solid and striated. Zocecial apertures polygonal, commonly hexagonal, arranged in
transverse and diagonally intersecting series, the first predominating, and both less
regular than usual for the genus. Here and there the presence of one or more
small cells (?abortive zocecia) may cause considerable interruption in the ordinary
arrangement. On an average nineteen or twenty apertures in 5 mm. diagonally,
and nine or ten in 2 mm. transversely. Walls very thin, the thickness about equal
on all sides. Non-poriferous margin very inconspicuous.

Of internal characters the most striking are (1) the unusual tenuity of the walls,
and (2) the erectness of the zocecial tubes. Tangential sections greatly resemble
such sections of certain Trepostomata (e. g. Monotrypella quadrata Rominger, sp.).

The comparatively irregular arrangement of the zocecial apertures, their
angular form, and the fact that their also thinner walls commonly form hexagonal
or polygonal instead of subrhomboidal spaces, distinguishes this species from FE. fal-
ciformis (Ptilodictya falciformis Nicholson) of the Cincinnati group. In other respects,
especially in the shape of the zoarium, the two species resemble each other very
greatly. Embedded in the limestone, with only a portion of the surface exposed,
E. angularis might very easily be mistaken for some monticuliporoid. Not so,
however, with E. subrecta, which abounds at the same localities though not at the
same geological horizon. The zoarium of the latter is always straighter, and the
zocecial apertures quite different.

Formation and locality—Rare in the Trenton limestone at Minneapolis, Minnesota.

EscHaropora susrecta Ulrich.
PLATE XII, FIGS. 5-29.

Ptilodictya subrecta ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn, p. 63.

Zoarium simple, flattened, straight or slightly curved, 12 to 40 mm. or more
long, 1.3 to 9.0 mm. wide, the two faces obscurely ridge-shaped, or evenly convex.
Average size about 25 mm. long, and 2.5 mm. wide in the upper half. Greatest
thickness varying with age from 0.6 to 1.5 mm. Lower half tapering gradually to
to the pointed basal articulating extremity, the latter often turning a little to one
side, subcylindrical, finely striated longitudinally, the grooves widening slowly
BRYOZOA. . 169

Escharopora.]

upward till they graduate into the elongate, confluent zocecial apertures. Arrange-
ment and appearance of zocecial apertures and interspaces varying with age. In young
examples, or those less than 25 mm. in length, and these seem to be by far the most
abundant, the surface appears as in figures 18 to 21. In these the zocecial apertures
over the entire surface, excepting near the base and along the edges, are elongate
elliptical, sometimes almost acute at the ends, and arranged between alternately
converging and receding ridges, which, failing to close around the ends of the
apertures, permit confluence between them through a narrow channel. The result
is a very pronounced longitudinal arrangement, though the diagonal rows, and
sometimes the transverse as well, are scarcely less evident and regular. Measuring
lengthwise there are about eleven zocecial apertures in 5 mm.; diagonally nine or
ten in 2.5 mm.; transversely six of the central rows inl mm. The marginal rows
are always larger, and occasionally have the oblique character shown in fig. 21. In
specimens 25 mm. long the upper extremity will already indicate the changes that
took place in later growth. The shallow channel connecting the zocecial apertures
is gradually lost through the closer convergence of the enclosing ridges, till at last
we have a simple ridge-like separating wall as shown in figs. 28 and 24. These
figures show further that the apertures are now wider, with only five in 1 mm.
transversely, and of subrhomboidal or hexagonal form. The increased width is
accounted for partly by the loss of the channels, and the remainder by the increased
circumference of the zoarium. The largest specimens usually exhibit a central row
of small monticules. In some there are two irregularly alternating rows, while in
the fragmentary original of fig. 17, there are three rows. The last specimen is
peculiar also in having an arrangement of the zocecial apertures foreshadowing true
Ptilodictya, namely, oblique “pinnate” rows predominate on the spaces between the
outer monticules and the edges of the frond, yet over the central part of the surface
the usual diagonally intersecting series prevail.

All the changes produced by age are chiefly apparent in the upper half-of the
zoarium, the appearance of the early stages being more or less preserved in the
basal portions. Still, very old and thick examples, like the original of figs. 15 and
22, are likely to develope mesopores here in place of mere channels between the
zocecial apertures.

Of internal characters shown in the excellent and instructive sections illus-
trated, I wish to point out (1) the elongate form of the primitive cell, (2) its shape
just before being roofed over to form the primitive aperture, and (3) the two at first

*aistinct then coalescing lines in the transverse interspaces. (See upper parts of

figs. 25 and26.)
170 ‘THE PALEONTOLOGY OF MINNESOTA.

{Escharopora.

In 1886 I believed this species to be a close relative and, perhaps, the western
representative of Hall’s E. recta. Since making my final investigations, with aug-
mented material in all stages of growth, much of it in an excellent state of preser-
vation, I find that the relationship is more remote than it seemed at first. Although
Ihave not had an opportunity of examining authentic examples of E. recta, Hall’s
original figures are sufficiently diagnostic to warrant us in saying that the New
York species has zocecial apertures agreeing both in shape and arrangement with
those of EF. falciformis (Nicholson) and the closely related E. acuminata (James).
The last is the form referred to (loc. cit.) as occurring “in the lower beds of the
Cincinnati group (Utica shale ?) in Ohio.” The form mentioned at the same time as
found in Tennessee (“Glade” limestone) greatly resembles E. acuminata, but as I
have not yet examined its interior structure, I cannot say that it is really the same.
Whatever it may turn out to be I am satisfied that it is distinct from E. subrecta.
Comparing ordinary examples of the Minnesota species with any of these forms,
indeed with all of the known simple species of the genus, we find that in none
of the latter, save for a short distance: above the pointed base, are the zocecial-
apertures confluent longitudinally, i. e. connected by narrow channels, as is the case
in E. subrecta. Nor do any of them exhibit as much difference in the size of the
marginal and central rows of apertures. Of unbranched species, E. subrecta is also
the only one known to me in which the primitive cell assumes the peculiar clavi-
form shape shown in figs. 25 and 26. In most of the other species, perhaps all save
E. angularis, the hemisepta are more pronounced. These two features alone are
sufficient in distinguishing thin sections of E. subrecta. Compared with the branch-
ing forms, we find one, and it is associated in the same beds, that agrees in many
respects. This is the next described E. confluens, having confluent zocecial apertures,
a similar difference in the size of the marginal and central rows, and an internal
structure nearer that of H. subrecta than any other species. But the zocecial
apertures are wider, a fact noticeable enough to enable one to distinguish the
merest fragments. There is, of course, no likelihood of confusion when complete
zoaria are available.

‘Formation and locality.—Common in the middle third of the Trenton shales at Minneapolis and
other localities in the state, and Decorah, Iowa. Perhaps, also, in the lower third of the shales, but rare
in these and smaller than usual. A single example collected by Mr. Charles Schuchert from the ‘‘ Lower
Blue beds” near Beloit, Wisconsin, seems to belong to this species.

Mus. Reg. Nos. 5929, 7558 and 7597.
BRYOZOA. 171

Escharopora.]

EscHAROPORA CONFLUENS 1. Sp.

PLATE XIII, FIGS. 1-12.

Zoarium branching, the smallest seen less than 25 mm. high, with the branches
averaging about 2.5 mm. in width; the largest fragments indicate a hight of from
80 to 120 mm., and in these the width of the branches varies from 4to8 mm. The
two surfaces of the branches are generally obtusely ridge-shaped, and in the largest"a
. row of monticules, or simply clusters of large cells, occurs on the summit of the
ridge. Edges thin and sharp, commonly with a coarsely striated or pitted narrow
border. Through all stages, though less distinct in the oldest, the zocecial apertures
are narrow and appear to be drawn out at the ends so as to connect by means of a
narrow channel. This confluent character of the zocecial apertures is better shown
and more regular in the central rows, where they are also narrower and on ‘the
whole considerably smaller than towardthe margins. (See fig. 5.) In the central
rows, ten in 5 mm. lengthwise ; eighteen or nineteen in 5 mm. diagonally, and five
and one-half in] mm., and ten in 2 mm. transversely; of longitudinal rows there
are nineteen or twenty in 2 mm.

Tangential sections show that the base of the zowcia, excepting those in the mar-
ginal rows, is bounded by very thin, straight, longitudinal walls, and equally thin
transverse partitions. This portion of the zocecium therefore may be described as
a parallelogram, with the length and breadth respectively as four is to one. At
about the middle of the hight of the primitive cell its sides have spread a little and
the ends contracted in a corresponding degree. Just as the posterior half is about
to be roofed over two projections from the side walls, at a points a little behind the
middle, gradually converge until they meet and thereby cut off and enclose the ellip-
tical primitive aperture. In the succeeding stages the principal change is a reduc-
tion in the size of the apertures, caused by an internal deposit. These stages are all
shown in figs. 6, 7 and 8, but to insure a trustworthy idea of the internal structure
of the species, they should be studied in connection with figs. 10 and 11.

Compared with associated Bryozoa, the next described E. (?) limitaris only will
be found difficult to distinguish. This, however, is due chiefly to the imperfect pre-
servation of the surface of most specimens. Good examples of the latter are quickly
distinguished by the different character of the longitudinal interspaces, these being
occupied by one elongated pit or two smaller ones.

The zoarium of E. subrecta is always strictly of the simple type, and never
branches except under abnormal conditions.

Specimens of this and the following species were catalogued by me in 1886 as
Ptilodictya ramosa Ulrich (now Escharopora ramosa).* Comparison with the Kentucky

 

*PFourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 102.
172 THE PALEONTOLOGY OF MINNESOTA. oer
: [Escharopora.

and Tennessee tpyes of that species was not possible before the following year, when
I became satified that the Minnesota specimens were really quite different, though
similar in their growth. In E. ramosa the zoccial apertures are set into regularly
hexagonal spaces, and are in no sense to be called “confluent.”

Formation and locality.—A pparently restricted to the middle third of the Trenton shales, at Minne-
apolis, Minnesota. Fragments of a very similar, perhaps identical, species have been ‘observed in the
‘* Pierce” limestone at Murfreesboro, Tennessee.

Mus. Req. No. 8208.

EscHAROPORA (?) LIMITARIS, ”. $p. Or var.

PLATE XIII, FIGS. 12 and 13.

Under this name I propose to arrange a form that may well be regarded as the
beginning of the branching section of the genus Phwnopora, Hall. I would have
placed it under that genus but for the fact that I found it impossible to draw
a satisfactory line between it and E. confluens. Ordinarily the branches of the
present form are smaller and more evenly convex, their edges less sharp, and with a
wider non-poriferous border than in typical E. confluens; but in other specimens,
one in particular, the shape and general aspect of the zoarium is precisely as in the
most typical examples of the species. The single constant peculiarity of E. ( ?) limi-
taris consists in the development of an elevated rim at the ends of the zoccial
apertures, causing them to lose their confluent character, and to assume a definite
elliptical shape. At the same time the “channel” has been transformed into an
elongated inter-apertural pit. Frequently, instead of the single long pit, the space
is divided into two short ones, as in Phenopora wilmingtonensis, and P. incipiens.

The usual appearance of the surface may be imagined when I say that it is a
intermediate between the appearances represented in fig. 20, plate XII, and fig. 5,
plate XIII, on the one side, and figs. 14 and 23, plate XIII, on the other.

 

Fia@. 9. ‘Escharopora (?) imitaris ULRIcH. a, small part of ‘tangential section, x50, showing struc-
ture immediately beneath the point of bifurcation; 6. another portion of same where the zoarial margins
are parallel. -
BRYOZOA. . 173

- Phenopora.]

As shown in the accompanying cuts, the internal structure brought out in
tangential sections is often almost exactly as in Ph. incipiens (plate XIII, fig. 17);
‘other sections, however, in portions at least, show a structure more in accordance
with fig. 7, plate XIII. .

It is evident that E. (?) limitaris and E. confluens are varieties of one species,
but because of their intermediate position between Escharopora and Phenopora, it
is scarcely advisable to decide now which of the two names shall take the rank of a
species, and which that of a variety. Such decisions should be deferred till we are
better acquainted with the developmental history of fossil Bryozoa.

Formation and locality Not uncommon in the lowest third of the Trenton shales, at Minneapolis,
Minnesota. Also in the middle third of the shales at the same locality, but less common and of more
robust growth. A single specimen was observed among a lot of Bryozoa marking the lower shales,
collected by Messrs. Schuchert and Scofield, near Preston, Minnesota

Mus. Reg. No. 5930.

Genus PHAXNOPORA, Hall. :

Pheenopora, HALL, 1852, Pal. N. Y., vol. ii, p. 46; ULRton, 1882, Jour. Cin. Soc. Nat. Hist., vol. v.
p. 152, and 1890, Geol. Sur. II1., vol. viii, p. 392; ForRsTE, 1887, Bull.
Sci. Lab. Denison University, vol. ii, p. 157.

Zoaria bifoliate, simple or branching, the base pointed and articulating into a
small basal expansion, the same as in Péilodictya and E’scharopora. Zocecial arrange-
ment regular, in longitudinal, diagonally intersecting and transverse rows, with
either the longitudinal or the diagonal series predominant. Two mesopores behind
each zoccial aperture, one on each side, or one behind the other. Primitive cells
elongate, commonly oblique or lozenge-shaped, at other times with the ends rectan-
gular, always arranged between straight, longitudinal walls. Monticules, or mere
clusters of large cells and mesopores, present when zoaria are wide enough.

Type: Phenopora explanata Hall, 1852, Pal. N. Y., vol. ii, p. 46.

From the above description it is obvious that the presence of the two mesopores
is the only character to be relied upon in distinguishing the genus from Escharopora
and Ptilodictya. The genus attains its highest development in the Clinton group, and
in most of the species from that horizon the primitive cell has a peculiar oblique
shape that is not seen in the Lower Silurian representatives of the genus, nor in any
species of Escharopora, but is not uncommon among true Upper Silurian Pétilodictya.
As might be expected, it is among the unbranched species that the greatest resem-
blance to Ptilodictya obtains. Indeed, such species as Ph. ensiformis Hall, and Ph.
lonsdalei (Ptilodictya lonsdalei Vine) are in every respect, save in this that they possess
the characteristic mesopores, precisely like narrow species of Ptilodictya.

In the following classification I have arranged the species in sections the same
as under ‘Escharopora. Except in one instance, I have not been able to obtain
174 THE PALEONTOLOGY OF MINNESOTA.

[Pheenopora.

specimens of the European species, described mainly as Ptilodictya, that I suspect
to belong to this genus. Under the circumstances it would not be safe to include
them.

Section a, zoaria simple, without monticules.

Pheenopora ensiformis Hall, Clinton group, New York, Canada, Ohio and Indiana.
_P. lonsdalei (Ptilodictya lonsdalei Vine), Wenlock shales, England.
P. tenuis Hall, Lower Helderberg group, New York.

Section }, zoaria simple, with monticules.

Pheenopora bipunctata (Ptilodictya bipunctata (Van Cleve) Hall,) Clinton group, Ohio.
P. constellata Hall, Clinton group, New York and Canada.

P. expansa Hall and Whitfield, Clinton group, Ohio.

P. punctata (Ptilodictya punctata Nicholson and Hinde), Clinton group, Canada.

P. superba (Ptilodictya superba Billings), Anticosti group, Anticosti.

P. wilmingtonensis Ulrich, Cincinnati group, Illinois.

Section c. zoaria branching.

Pheenopora excellens{Ptilodictya excellens Billings), Anticosti group, Anticosti. -
P. explanata Hall, Clinton group, New York and Canada.

P. fimbriata (Ptilodictya fimbriata James), Clinton group, Ohio.

P. incipiens Ulrich, Trenton group, Canada and Vermont.

P. lindstreemi Ulrich, Upper Silurian, Gotland.

P. magna (Stictopora magna Hall and Whitfield), Clinton group, Ohio.

P. multifida (Stictopora multifida (Van Cleve) Hall), Clinton group, Ohio.

Though fully convinced that some of these species are synonymous, it seemed
best to retain all names until an opportunity offers to treat the genus in a mono-
graphical way.

PHZENOPORA INCIPIENS N. Sp.

PLATE XIII, FIGS. 14-17.

Zoarium small, dividing dichotomously at rather long intervals; basal extremity
long, slender, subcylindrical, with fewer and more elongate zocecial apertures than
above the first bifurcation. Branches 1.5 to 2.0 mm. wide, compressed, rigid, edges
sharp, parallel, with moderately developed striato-punctate, non-poriferous border.
Zocecia in from twelve to fifteen alternating ranges, very regularly arranged in long-
itudinal, diagonally intersecting and transverse rows, with respectively eleven in
5 mm., ten in 2.5 mm., and fivein] mm. Zoccial apertures of equal size, elliptical,
enclosed in a minutely papillose rim or peristome, the latter slightly depressed at
the ends, and generally in contact with each other at four points, so that with a side-
light the apertures may appear as arranged between alternately converging and
diverging raised lines. End interspaces elongate, depressed, commonly occupied by
two mesopores, in other cases by three, and rarely, except in the marginal rows,
by four or more now in double rows; always disposed in*a longitudinal manner.

.

Non-pouiferous border occupied by two or more rows of mesopores.
BRYOZOA. 175

Phenopora.]

This form is easily distinguished from all the branching Clinton group species
of the genus by the longitudinal arrangement of the mesopores. It is, however,
especially in its internal structure, very similar to, and perhaps a descendant of,
Escharopora (?) limitaris. Still, its branches are narrower and more rigid, and there
is not that difference in the size of the central and marginal rows of zoccia that
pertains to that Minnesota species.

Formation and locality—Trenton limestone, Montreal, Canada, and Chimney Point, ‘Vermont,
Recently a fragment apparently identical with the eastern types of the species was collected at St. Paul,
Minnesota, by the author, in the Galena shales. :

Collectors, Mr. T. C. Curry and Prof. Henry M., Seely.

PHANOPORA WILMINGTONENSIS 1. Sp. ©

PLATE XIII, FIGS. 22-26,

Zoarium a simple lanceolate frond, straight or slightly curved, tapering to a
point below, 40 to 100 mm. or more in length, 6 to 24 mm. wide, and 1.0 to 2.5 mm.
thick at the center; edges acute, non-poriferous margin inconspicuous, surfaces
gently convex, sometimes a little flattened on each side of the center, exhibiting,
according to the width of the frond, from one to ten rows of low monticules. The
latter occur at intervals of 2 or 3 mm., are usually arranged in rather irregular
longitudinal and diagonal rows, and occupied by greater or smaller aggregations of
mesopores and zocecia, the latter of slightly larger size than the average. Zocecial
apertures subcircular or ovate, arranged in regular diagonally intersecting and
transverse rows ; often, especially in the lower half of the zoarium, with the enclosing
rim depressed at the ends, in which case they appear to be longitudinally confluent.
Longitudinal interspaces depressed, generally with two small mesopores, one just in
front of, the other immediately behind each aperture. Toward the center of the
monticules the number of the mesopores in each interspace is gradually increased
to four or more. Measuring lengthwise, about twelve apertures in a direct line § mm.
long, and twenty-three or twenty-four of the transverse rows in the same distance ;
diagonally, twenty, and transversely twenty-three or twenty-four in 5 mm.

In tangential sections the base of the primitive cells is greatly elongate and
bounded by subparallel sides and slightly oblique end walls. Very soon after, the
anterior two-thirds is swollen and a curved hemiseptum thrown out from one side,
which continues till it joins the opposite wall, thus enclosing the primitive aperture.
Preceding this the walls are very thin, but now they add to their thickness by
internal deposit. At the same time the aperture assumes a more rounded shape, the
walls approach laterally so that each cell is, normally, in contact. with six of its
neighbors. Between these points there is a triangular open space or mesopore.
176 THE PALEONTOLOGY OF MINNESOTA.
= [Arthropora

The walls consist, first, of the original, transversely lined (? minutely perforated)
investment, and, second, of an inner laminated deposit (see fig: 25). This structure
prevails in all the typical genera of the Ptilodictyonide, but, unfortunately is rarely
preserved.

Every important feature noticed in vertical sections is represented in fig. 26.

When plate XIII was lithographed the specimen thereon illustrated was the only
one then available. When, several months later, the remainder of my collections
from Wilmington, Illinois, was unpacked, I was fortunate enough to find seven more
examples, three of them with the pointed basal extremity.

The presence of mesopores distinguishes this species from Lower Silurian
Escharopora, like E. maculata Ulrich, while their longitudinal arrangement serves to
separate it from the unbranched Upper Silurian species of Phenopora.

Formation and locality.—Upper beds of the Hudson River group, at Wilmington, Illinois.

Genus ARTHROPORA, Ulrich.

Ptilodictya and Stictopora ( part.), of several authors.
Arthropora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p..152; S. A. MILLER, 1889, North Amer.
Geol. and Pal., p. 293; ULRICH, 1890, Geol. Surv. Ill., vol. viii, p. 393.

Zoaria bushy, spreading in a plane, composed of numerous, essentially equal
segments ;- joints simple, bifurcating, or with several short lateral branchlets, the
extremities solid and rounded for articulation with succeeding segments. Zoccial
apertures elliptical, surrounded by a delicate peristome. Interspaces with one or
more thread-like ridges, variously disposed, sometimes short and vermicular, at other
times forming continuous longitudinal wavy lines, or ranged in a concentric manner
about the apertures. Peristomes and ridges each with a row of minute papille.
Interior with the primitive cell elongate, narrow, one or both hemisepta, and lined
with minute dots (? median tubuli) between the zocecia in. the peripheral region.
Mesial laminz zigzag in transverse sections, without “median tubuli.”

Type: Arthropora shafferi (Stictopora shafferi Meek). Range, from base of
Trenton formation to top of Hudson River group.

This genus is closely related to Graptodictya, the only difference being that in
the species of that genus the zoarium is continuous above the basal articulation,
while in Arthropora it is divided into subequal joints. In certain of the internal
characters, (e. g. the rows of interstitial dots) we are reminded of the Rhinidictyonide,
but the general agreement with the Ptilodictyonide, especially in the absence of
minute tubuli between the mesial lamin, precludes all likelihood of near relation-
ship with Rhinidictya.
Wiveaues BRYOZOA. 177

_ The three species next following and A. shafferi (Meek) are the only species so
far published of which we know positively that they belong to Arthropora. There
are, however, at least three other distinguishable forms in the Cincinnati group of
Ohio, Indiana and Kentucky, each marking a particular horizon in the group. Most
of the species are abundant, but it is exceedingly rare to find any number of the seg-
ments still joined together, or lying in their original order.

ARTHROPORA SIMPLEX Ulrich.
PLATE XIV, FIGS. 12-21.

Arthropora simplex ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 65.

Zoarium jointed, rarely found except as isolated segments. Normally developed,
the segments are narrow, more or less compressed, unbranched, straight stems,
rounded and solid at each end, with sharp edges and striated non-poriferous border ;
12 to 19 mm. long (average length about 18 mm.), 1.0 to 1.8 mm. wide, and always
less than 1.0 mm. in thickness. The basal or primary segment is irregularly
branched, and occasionally some of the succeeding segments are divided, but such
divisions are evidently abnormal. A single specimen preserves several joints in
their natural position, From this it appears that, as a rule, the upper extremity of
each segment articulated with two succeeding segments. Basal segments thickest,
sometimes nearly cylindrical, their superficial characters obscured, the peristomes
and interstitial ridges thickened and the zocecial apertures reduced in size through
age. In the younger segments, and most specimens are to be so classed, the
characters are as follows: zocecia very regularly arranged in transverse and
diagonally intersecting series, with five in 1 mm. transversely, and eleven or
twelve in 3 mm. diagonally ; twenty-four to twenty-six of the transverse rows
in 5 mm. longitudinally. Zocecial apertures elliptical, surrounded by a very
thin, granose peristome. The latter is easily overlooked, strongly depressed at the
sides, but elevated and prolonged at each end, in most cases not far enough to con-
nect succeeding apertures ; separating the longitudinal rows an elevated, thin, papil-
lose, wavy ridge. In passing around the zocecial apertures these ridges alternately
diverge and converge, two coming close together, often even uniting, in the spaces
between the sides of the apertures. In many segments only the raised ends of the
inner depressed ring of papille are distinguishable. In these cases the longitudinal
ridges combine in front and behind the apertures so as to produce an appearance

similar to fig. 22, plate XIV.

—1
178 “THE PALEONTOLOGY OF MINNESOTA.
% ({Anthropora.

In figures 21 a, b, c, I have endeavored to show all the characters of the zocecia
that are to be brought out in tangential sections. The right sides of a and b repre-
sent the structure just beneath the surface, while the left sides show it at a deeper
level in the section. In 21 ¢ only the primitive or prostrate portion of the zocecia is
shown.

The unbranched character of the segments of this species, as well as their greater
length, will distinguish them at once from all other species of the genus.

Formation and locality.—Very abundant in the lower and middle thirds of the Trenton shales, at
Minneapolis, St. Paul, Fountain and other localities in Minnesota; Decorah, Iowa.

Mus. Reg. Nos. 5933, 8075.

ANTHROPORA BIFURCATA 1. Sp.

PLATE XIV, FIGS. 22-25.

Segments small, thin, with sharp edges and rather wide non-poriferous border,
the lower ones bifurcating, usually only once; so far as observed not over 8 mm.
-long, and from 1.2 to 1.8 mm. wide; the upper joints shorter, their length occa-
sionally less than 5 mm., bifurcating, or with a single lobe-like projection on one or
both sides. Young segments with comparatively large, ovate zocecial apertures, not
very regularly arranged in longitudinal and diagonally intersecting series, with
about nine in 3 mm. lengthwise, and five in 1 mm. diagonally. Apertures enclosed
in distinct granulose rims, connecting longitudinally. Interspaces depressed, some-
times with a few indistinct strie. With age the zocecial apertures become more
circular and smaller, and the peristomes and connecting ridges thicker.

This species is related to A. shafferi (Meek) but differs in having only one ridge
or line in the interspaces, instead of from one to four. A. simplex has longer and
unbranched segments, while A. reversa has a peculiar horseshoe-shaped ridge about

its zocecial apertures.

Formation and locality.—Detached segments rather common in the Galena shales and in the upper
third of the Trenton shales at St. Paul, and Cannon Falls, Minnesota. A closely allied species, perhaps it
is identical, in the Trenton limestone of Kentucky, Tennessee, and Canada,

Mus. Rey. No. 8108.

ARTHROPORA REVERSA 2. Sp.

PLATE XIV, FIG. 26.

Of this species I have seen only two segments, but their superficial aspect is so
distinctive that I do not hesitate in proposing a new name for them. One of these
is 8 mm. long, and divides dichotomously about midway the length. The two forks
are of the same strength as the lower half, averaging 1.2 mm. wide, the three
extremities abrupt and tipped for articulation with the preceding and succeeding

\
Stictoporella.] . BRYOZOA. 179

segments. The other, apparently the basal or primary segment, is pointed below
trifurcately divided 4 mm. above the lower extremity, with the three branches of
equal strength and the central one again divided, this time merely bifurcating, at
its upper end; total length 8 mm., width about 10mm. The zoarial growth and
general aspect of the segments seems therefore to be precisely as in A. bifurcata.
Zocecial apertures small, subcircular, separated from each other by spaces fully
equalling their diameter ; arranged in rather irregular, more or less oblique trans-
verse series, about six in 1 mm., and in six to eight, more regular, longitudinal rows,
with twelve to fourteen in 3mm. Immediate border of apertures formed by a ring
of very minute granules. This ring is depressed except at the lower end, so that it
is not likely to be seen save under the most favorable circumstances. The lower
end is commonly prolonged into one or two short rows of granules, perhaps extend-
ing completely across the end interspaces. The most striking peculiarity of the
species is a horseshoe-shaped ridge, open below, which, in the usual state of preser-
vation, appears to enclose the sides and upper end of each zoccial aperture. This
ridge is papillose, thick, and strongly elevated in the middle (in front of each aper-
ture) gradually tapering to the ends. The strong elevation in front of the apertures,
causing them to appear as oblique and turned backward, suggested the name reversa.
The ends of the horseshoe ridge may be free, (see fig. 26) or they may unite with the
sides of the one next beneath. Non-poriferous border rather wide, with distinct,
oblique rows of papille. /

Formation and locality.—Upper third of the Trenton shales, at St. Paul, Minnesota. Recent collec-

tions made at this locality from this horizon and the overlying Galena shales afford a considerable number
of detached segments agreeing in all essential features with the described types of the species.

Mus. Reg. No. 8109.

Genus STICTOPORELLA, Ulrich.

.

Stictoporella, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, pp. 152 and 169; and 1890, Geol Surv.
Il., vol. viii, p. 394; Vine, 1884, Fourth Rep. Brit. Assoc. on Foss.

Poly., p. 44; Mr~umr, 1889, North Amer. Geol. and Pal., p. 325.
Zoaria bifoliate, growing from a broad basal expansion into narrow, parallel-
margined, branching stipes, simple leaf-like fronds, or cribrose expansions. Zoccia
with the primitive portion tubular, unusually long; generally without hemisepta, the
inferior one only occasionally present. Apertures elliptical, placed at the bottom of
a sloping area, the latter usually polygonal. More or less numerous, thick-walled,
untabulated mesopores occur between the zocecial apertures and line the zoarial
margins. Macule, composed of clustered mesopores, and sometimes of zocecial aper-

tures of larger size than the average, commonly scattered over the surface of the

frondescent species.
180 THE PALEONTOLOGY OF MINNESOTA.
‘ : {Stictoporella.

Tangential sections of favorably preserved specimens show that both the zocecia
and mesopores are separated from each other by a sharply defined line of minute
pore-like dots. True median tubuli and diaphragms wanting.

Type: &. interstincta Ulrich. Range, Lower Trenton to Chester.

For remarks on the relations and systematic position of this genus see ante p. 162.

The range of zoarial diversity allowed in this genus is unusually comprehensive.
Perhaps it is too much so, and that the cribrose species ought to be distinguished
generically. Most certainly they look very different from the others and are, I grant,
as much entitled to generic separation as Clathropora, Hall, Coscinium, Keyserling,
and other genera that might be mentioned, all differing from related genera chiefly
or solely in the cribrose character of the zoaria. Though inclined to favor a sepa-
ration, I have decided to leave them with Stictoporella for the present.

CLASSIFICATION OF AMERICAN SPECIES.

Section a: zoarium branching.

Stictoporella interstincta Ulrich, Utica horizon, Cincinnati group, Kentucky.
S. angularis Ulrich, base of Trenton shales, Minnesota. /

S. angularis var. intermedia Ulrich, base of Trenton shales, Minnesota.

S. dumosa Ulrich, Trenton shales, Minnesota.

S. rigida Ulrich, Trenton shales, Minnesota.

Section b: zoarium wide, leaf-like, with macule. °

Stictoporella frondifera Ulrich, base of Trenton shales, Minnesota.
S. ? basalis Ulrich, Keokuk group, Illinois, Iowa.
S. ? undulata Ulrich, Chester group, Kentucky, Illinois.

Section c: zoarium cribrose.

Stictoporella cribrosa Ulrich, middle Trenton shales, Minnesota.

?Clathropora flabellata Hall, Trenton, Wisconsin.

Stictoporella proavia (Coscinium proavium Billings, ? Eichwald), Trenton, Canada.
S. n. sp.(with smaller meshes than in the others), ‘‘ Pierce” limestone, Tennessee.

STICTOPORELLA RIGIDA Ulrich.
PLATE XI, FIGS. 20 and 21.

Sticloporella rigida ULRICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 188.

Original description: “Zoarium a narrow branching, bifoliar stipe. Branches
flattened, 1.0 mm. or a litle more wide, with straight parallel and sharp margins,
acutely elliptical in cross-section. Zocecia in seven to nine or ten rows on each face,
their apertures arranged in very regular longitudinal and diagonally intersecting
series, with sixteen or seventeen in 5 mm. lengthwise and four in 1 mm. obliquely.
Apertures elliptical, 0.2 mm. long, half that wide, impressed, the sloping area narrow
for this genus, and appearing sometimes a little oblique because of a slight elevation
of the posterior border ; those in the marginal rows are directed slightly outward.
Stictoporella.] BRYODO & 181

Between the ends of succeeding zocecial apertures one or two small mesopores.
There is usually a row of these small pores along the border of the branches. Inter-
Spaces narrowly rounded or ridge-shaped, comparatively thin.”

This neat species is near S. interstincta from the Utica horizon of the Hudson
River group, but has somewhat narrower branches, fewer mesopores, and much thin-
ner walls. In 8. angularis the walls are much thicker, branches wider, sloping areas
about the zocecial apertures polygonal, and the mesopores less numerous and irregu-
larly distributed. S. dumosa has wider and oftener divided branches.

Formation and locality.—Rare in the lower part of the upper third of the Trenton shales, at St. Paul,
Cannon Falls, and near Fountain, Minnesota.

STICTOPORELLA DUMOSA n, Sp.

(Not figured.)

Zoarium forming bushy masses, as much as 100 mm. in diameter and 50 mm.
high, consisting of very irregularly divided, free or coalescing, small branches, 1.5 to
2.0 mm. in width, and usually less than 0.5 mm. in thickness. Zocecial apertures
subcircular or elliptical, set into rather wide sloping areas of polygonal or rounded
outline, the shape depending upon the number of mesopores present. Arrangement
rather irregular; occasionally longitudinal rows, with the mesopores between the
ends of the zocecial apertures, prevail, in which case the surface appearance is much
the same asin S. rigida. More commonly, however, a diagonal arrangement predom-
inates, with the mesopores distributed more at random. In these, especially when
the mesopores happen to be fewer than usual, the general appearance is much more
like that of S. angularis. Where the arrangement is the most regular there are ten
or eleven zocecial-apertures in 3 mm. diagonally, and about eight in the same space
longitudinally. Apertures often closed by a slightly convex plate, in which a minute
subcentral perforation may be détected. Walls ridge-shaped, generally wider than
the diameter of the zocecial apertures. Mesopores varying in number; sometimes a
fragment will show about one only to each zocecium, while others may have them
three or four times as numerous. Edges sharp, generally exhibiting two or three
rows of mesopores.

Internal structure, especially in transverse and vertical sections, very similar to
that of S.cribrosa. In tangential sections the mesopores are not as distinct, and the
divisional line between the zocecia less sharply defined, than in similar sections of
that species.

As a rule, I do not favor descriptions of species without illustrations, but in this
case the form is so easily recognized that the omission may be pardoned. Com-
pared with S. angularis it is distinguished by its more irregular and stronger growth,
182 THE PALEONTOLOGY OF MINNESOTA.
[Stictoporella.

and more abundant mesopores. The occasional inosculation of the branches points
toa relationship with S. cribrosa, and this is further evidenced by the agreement in
their internal structure. The position of the species is probably intermediate between
S. angularis and S. cribrosa.

Formation and locality—Upper third of the Trenton shales at St. Paul, Minnesota.
Mus. Reg. No. 8110.

STICTOPORELLA ANGULARIS Ulrich. .
PLATE XI, FIGS. 1-3, 6, and 8-11.

Stictoporella angularis ULRicu, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p, 71.

Zoarium branching dichotomously at intervals varying from 4 to 10 mm.; branches
more or less compressed, 1.5 to 3.0 mm. wide, 0.7 to 2.0 mm. thick, with sharp or nar-
rowly rounded, subparallel edges. Zocecial apertures small, subcircular, set into wide
sloping polygonal areas, with the subrhomboidal and hexagonal shapes commonest.
Walls ridge-shaped, angular in the middle, their thickness usually greater than the
- diameter of the apertures. Zocecial apertures arranged in moderately regular
curved diagonally intersecting series, nine in 2.5 mm. When longitudinal rows are
to be made out (as in upper part of fig. 6) six are to be counted in the same space
lengthwise. Mesopores comparatively few, small, sometimes appearing to be absent
entirely on parts of the central three-fifths of the surface, while for some distance
‘above or beneath such a spot they may occur regularly one to each zocecium. Near
the margins, however, some are always present, with one and occasonally two rows
bordering the edges. .

In tangential sections, showing the structure in the peripheral part of the zoa-
rium, the zoccial cavity is ovate, in old examples sometimes nearly closed by inter-
nal deposits of sclerenchyma, the interspaces always thick enough to separate the
cells by a distance greater than their diameter. Boundary line between the zocecia
and mesopores sharply defined, consisting of a crowded row of very minute, pore-like
dots. These, however, are not recognizable except in the most favorably preserved
specimens. Mesopores few, here completely filled with laminated sclerenchyma.

In vertical sections the thin-walled prostrate part of the zocecial-tube is long,
but, as is usual in this genus, this portion of the section appears irregular. Hemi-
septa absent. In turning to the surface the tube bends abruptly, and at once the
walls become very thick and marked with j-shaped lines representing the sloping
areas about the apertures at previous stages of growth.

The angularity of the zocecia, together with the unusual paucity of the meso-
pores, distinguishes this species from S. interstincta, S. rigida, S. dumosa and S. cribrosa.
Stictoporella.] BRYOZOA. 183

The broad, maculose zoaria of S. frondifera are not likely to be confounded, although

the two species are undoubtedly closely related. The following variety is good evi-
dence of that.

Formation and locality—Not uncommon in the lower third of the Trenton shales, at Minneapols, St.
Paul, and several localities in Goodhue and Filmore counties, Minnesota.

~ Mus. Reg. Nos. 5943. 7617.

STICTOPORELLA ANGULARIS, Var. INTERMEDIA 7”. var.

PLATE XI, FIGS. 4, 5 and 7.

This name is proposed provisionally for a form that is common at several locali-
ties in Filmore county, but rare in the more northern exposures of the same beds.
It differs from typical S. angularis, with which it is often associated, in forming wide,
irregular branches, the growth and size being in many instances precisely as in the
branching form of S. frondifera. At intervals the surface presents clusters of zocwcia
with thinner walls and larger apertures than usual. The mesopores are very few, in
most cases restricted to the center of the clusters mentioned. Here they may form
aggregations, but these are never, as far as observed, so extensive as in S. frondifera
One or two rows of them are also commonly present at the rounded margins of the
branches.

In having very few mesopores the variety agrees with S. angularis, while in its
wide branches and general aspect it is like S. JSrondifera. The name intermedia
alludes to its position between those species.

Formation and locality.x—Rare near the base of the Trenton shales, at Minneapolis, but common in
the same beds near Fountain, Lanesboro and Preston, all localities in Minnesota; also at Decorah, Iowa

Mus. Reg. Nos. 7597, 7599, 7984.

STICTOPORELLA FRONDIFERA Ulrich.

PLATE XI, FIGS. 12-19.

Stictoporella frondifera ULRICH, 1886. Fourteenth Ann. Rept. Geol. Nat. Hist. Surv. Minn., p. 72.

-Zoarium consisting of broad, irregularly branching, flabellate or undulate expan-
sions, 1 or 2 mm. in thickness, the whole attaining a hight of from 50 to 100 mm.
Edges rounded, with small pits (mesopores) in two or more rows. Surface with con-
spicuous macule consisting of greater or lesser aggregations of mesopores, sometimes
a hundred and more, generally about fifty or less. These macule are from 3 to 5 mm.
apart, sometimes arranged in rows, but oftener their distribution is decidedly irregular.
Between them the surface is occupied by the rounded zocecial apertures and meso-
pores, the latter small and unequally distributed, varying in number from one, two,
or even three to each of the former. Walls ridge-shaped, thick, usually nearly
184 THE PALEONTOLOGY OF MINNESOTA.
LStictoporella.

equalling the diameter of the zocecial apertures. Arrangement variable, rather
irregular, generally in diagonally intersecting series, with from fifteen to eighteen,
but averaging sixteen-in 5 mm. .

Internal structure, as shown in thin sections, very similar to that of S. angularis,
the only differences noticed resulting from the much greater development of
mesopores. ,

The much greater abundance of mesopores distinguishes this species from S.
angularis, var. intermedia, while the frondescent habit of its zoariym separates it
from all the other Lower Silurian species of the genus. Associated in the same
strata are Pachydictya foliata and Phyllodictya frondosa ?, two bifoliate species likewise
characterized by foliaceous zoaria. In other respects, however, they differ so obvi-
ously from S. frondifera, that detailed comparisons are rendered unnecessary.

_ Formation and locality.—Rather ‘abundant in the lower beds of the Trenton shales, at Minneapolis,
St. Paul, Preston, near Fountain, and other localities in the state where this horizon is exposed.

Mus. Reg. Nos. 5945, 5947, 7650.

STicTOPORELLA cRrIBRosA Ulrich,
PLATE X, FIGS, 21-25; PLATE XI, FIGS. 22 and 23.

Stictoporella? cribrosa ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 69.

Zoarium growing from a.small expanded basal attachment into thin erect
fronds, perhaps 50 mm. in diameter, composed of branches that inosculate at short
intervals till there is produced a broad expansion perforated at more or less regular
intervals by circular or elliptical fenestrules. Both sides of frond celluliferous,
consisting of two equal layers of cells grown together back to back in the manner
‘usual with bifoliate Bryozoa. Fenestrules elliptical, sometimes circular, varying
greatly, the average size about 1.8 mm. by 1.8 mm., or less than the width of the
branches ; but the same frond may show extremes like’ 1 mm. and less, and 3.5 mm.
Their arrangement is therefore more or less irregular, and taking other cribrose
species of the genus into consideration, this irregularity in the size and distribution
of the fenestrules is to be considered as a characteristic of the present species.
Width of branches generally 2.0 mm. or 2.5mm. but varying between the extremes
of 1.5 mm. and 3.1mm. Zocecial apertures small, subcircular or elliptical, the
average size about 0.1 mm. by 0.12 mm., set into sharply defined, polygonal or
rounded, sloping areas, about nine in 2.5mm. Mesopores small, numerous, often
completely isolating the zocecia. Generally, however, the latter are in contact with
each other at limited points. Around the fenestrules there is a band, 0.5 mm. or
less wide, occupied solely by mesopores. As in other ‘species of the genus the
185
Arthrostyllide. | BRYOZOA.

zocecial apertures are often closed by a convex plate, with or without a minute
subcentral perforation.

Tangential sections show that the polygonal boundary of the zoccia is marked
by a dark line, which under favorable preservation will probably consist of a row-of
exceedingly minute pore-like dots. Visceral cavity ovate or subcircular, generally
of less width than the walls. Mesopores numerous, of irregular shape and unequal
dimensions, often completely filled, or only preserving a very small central cavity.

Vertical sections show that the divisional lamin are somewhat flexuous, the
tubes at first thin-walled and prostrate, overlapping each other for some distance,
that they subsequently bend abruptly outward, and that their walls at the same
time are much thickened and marked with oblique lines parallel with the form of
the apertures. The mesopores appear as narrow open spaces when not entirely
filled by the secondary deposit of sclerenchyma. Diaphragms and hemisepta
wanting.

The Canadian Trenton limestone species identified by Billings with Eichwald’s
Coscinum proavium, is closely related to S. cribrosa, but differs in having narrower
branches, subequal and more regularly disposed fenestrules, and less numerous
mesopores. Another cribrose species, but in every respect smaller than these,
occurs in the “ Pierce” limestones at Murfreesboro, Tennessee. Still another Lower
Silurian bryozoan with inosculating branches has been described by Hall from the
Trenton rocks of northern Wisconsin.* He named it Clathropora flabellata, but both
the description and figures are entirely inadequate for anything like satisfactory
identification. It may belong to Clathopora, but Stictoporella is more likely to be
right. Then again it is not impossible that it is a Coscinella or even a Coscinum,
since in all of these paleozoic genera the zoarium is cribrose. Compared with the
characters shown in Hall’s figures, it is evident that he had before him a more
robust species, with branches and fenestrules much larger than in S. cribrosa.

Formation and locality.--Abundant in the middle third of the Trenton shales at Minneapolis and
St. Paul, Minnesota. The species seems to be restricted to this horizon.

Family ARTHROSTYLLIDA, Ulrich.

This interesting family of small Bryozoa is strongly represented in the Lower
Silurian rocks of Minnesota. On account of the minute proportions of most of them
their dismembered zoaria are generally to be found only by searching the'surface of
the slabs of fossiliferous limestone that occur so abundantly in certain parts of the
Trenton shales. These are often full of the separated joints. The most satisfactory

*Foster and Whitney's Report, vol. 2, p. 207, 1851.
186 THE PALEONTOLOGY OF MINNESOTA. pees,

specimens, however, are those which are obtained by picking over the residue of
washings of the shales themselves. These are better, not only because they can be
studied from all sides, but because their preservation is, in most cases, more favorable.

- Unfortunately, I had neither the time nor the opportunity of making extensive
washings of shales in Minnesota, and that method of collecting was employed to
only a very limited extent. Here and there a pound or two of unusually rich clay was
carried away and washed during leisure moments after my return home. One of
these packets proved to contain so many interesting things, and withal was so rich
in individuals, that it deserves mention. The shale was from the lower part of the
Galena shales, which, according to my reckoning, is the exact equivalent of the
Trenton limestone of New York. After washing away less than half its bulk nearly
two-thirds of the residue consisted of good fossils, of which the larger ones, mainly
species of Prasopora, Homotrypa, Callopora, Constellaria, Eridotrypa and some Brachi-
opoda, were separated by sifting the finer material away from them. A large pro-
portion of this fine material consisted of small fossils, among them five or six species
of Ostracoda, (most of them described in this volume as new) and at least eleven
species of small Bryozoa. Of the latter eight belong to the family under considera-
tion, two of them being species of Arthroclema, three of ‘Helopora, and three of
Nematopora.

The jointed character of the zoarium is the most conspicuous and perhaps also
the most important feature of the family. It is well shown in all the genera except.
Nematopora, in which articulation occurs only at the basal extremity, the zoarium
above the base being a dichotomously dividing, continuous stem. In Helopora, Hall,
Sceptropora and Arthrostylus, the segments are simple and terminally joined together,
and doubtlessly formed bushy zoaria. But in Arthroclema, Billings, the zoarium forms
a more or less plumose expansion, divisible into numerous primary, secondary and
tertiary segments, those of the first and second order being connected terminally
and ranged in straight lines. A deep socket occurs on one or two opposite sides of
each of the strong joints of the primary series and a shallow one in most of those of

the smaller secondary set, in which respectively the first of the series of the second
and third order is inserted.

The zocecia are arranged in a radial manner around a central axis and, excepting
-Arthrostylus in which one side is marked with longitudinal strice only, open on all
sides of the subcylindrical segments. In transverse sections the primitive portion
of the zocecia is wedge-shaped, but in longitudinal sections they often appear tubular.
The length of the tubes depends very largely upon the diameter of the segment, since
all of them reach the central axis. It is evident that the obliquity of the tubes also
has something to do with their relative lengths. They are, however, not to be con-
187
Arthrostylus.] BRYOZOA.

sidered tubular in the sense attaching to that term when applied to the Cyclostomata.
On the contrary they are no more so than are the zovecia of the most typical Rhinidic-
tyonide. In tangential sections they are oblong-quadrate or hexagonal in outline.
Hemisepta have not been observed, but rows of minute tubuli occur between the
walls of adjoining zocecia and sometimes in the longitudinal interspaces in the ves-
tibular region. A minute tube is also to be detected running from end to end through
the axis of the segments.

Respecting the position of the family the jointed character of the zoaria leads
us to look for its relationship first with the similarly constructed Cellariidw. The
latter embraces living forms chiefly, and of many of these I have secured specimens,
so that I am now in a position to speak intelligently upon their characters, as com-
pared with paleozoic forms. I would be glad to do this here were it not that I would
thereby interfere with my plans for a general work on inter-relation of bryozoan
types. It will probably be sufficient to say that the two families are distinguishable,
and that the relationship between them, if any exists, is almost certainly less inti-
mate than that between the Arthrostylide and Rhinidictyonide.

Aside from the wedge-shaped form of the primitive cells in the Arthrostylida,
which it is evident resulted necessarily from their radial arrangement about a linear
central axis, they are precisely like those of true Rhinidictya. They agree also in
possessing median tubuli between the walls of adjoining zoecia. Then again I am
convinced that the minute axial tube of the Arthrostylide is functionally identical
with the median tubuli between the mesial laminz that are such a characteristic
mark of the Rhinidictyonide. The jointed character of the zoarium even, is not
unknown in the latter since it pertains to Dicranopora, Ulrich, a genus that in all
other respects is precisely like Rhinidictya. Really, I find only one structural differ-
ence between the two families, and that is that while the zocecia in the Rhinidicty-
onide are arranged so as to form bifoliate zoaria—in other words, are disposed in
two equal expansions grown together back to back, they are arranged radially
around a central axis, forming subcylindrical zoaria, in the Arthrostylide.

Genus ARTHROSTYLUS, Ulrich.

Arthronema, ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, pp. 157 and 160 (not EsCHSCHOLTz,
who used the name for a genus of Colpodea).

Arthrostylus, ULRICH, 1888. Amer. Geologist, vol. i, p. 230; 1890, Jour. Cin. Soc. Nat. Hist., vol, xii,
p. 188; 1890, Ill. Geol. Sur., vol. viii, p. 400.

Zoaria bushy, branching dichotomously, the whole consisting of numerous,
exceedingly slender, subquadrate, equal segments, joined to each other by terminal
articulation. Zocecia arranged in three (perhaps more) rows, usually between
188 THE PALEONTOLOGY OF MINNESOTA.
[Arthrostylus.

longitudinal ridges; the tourth face, commonly the widest, with longitudinal striz
only.

Type: Arthronema tenue Ulrich (Helopora tenuis James), of the Utica horizon of
the Cincinnati group. (Jour. Cin. Soc. Nat. Hist., vol. v. p. 160, 1882.) The lower
fig. 16 on Plate III, represents a transverse section of this species. It should have
been been numbered 16a.

Besides the type species only three others are known to have the characters
demanded by this genus. Two of these are from the Trenton shales of Minnesota,
and are next described. The third species, A. curtus Ulrich, from the Hudson River
rocks of Ohio, is still a little doubtful, no further material having been found to
throw light upon the rather imperfect originals of the species.

ARTHROSTYLUS consuNcTUS Ulrich.
PLATE III, FIGS. 13 and 14.

Arthrostylus conjunctus ULRICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 189.

Original description. “ Zoarium jointed ; segments very slender, straight, needle-
shaped, 3 or 4 mm. long, quadrangular in cross-section, 0.25 mm. wide, 0.18 mm. thick,
with zocecial openings on three sides, the fourth being without them, but marked,
instead with four parallel longitudinal striz. _Zocecial apertures broad-oval, direct,
0.11 mm. long, 0.09 mm. wide, enclosed by a sharply marked peristome. Peristomes
of each row of apertures joined together by a thin ridge, having a length about equal
to the larger or outer diameter of the peristomes. Hight zocecial apertures in each
rowin2.5mm. A thin ridge on each side of the range of apertures of the obverse
face of the segment separates it from the lateral rows. Apertures usually arranged
alternately in the three rows.

“This species is closely related to A. tenuis James, sp., but is distinguished by
having the non-celliferous side narrower and with fewer stria, causing transverse
sections to be more nearly square. The A. obliquus differs in having oblique zocecial
apertures.”

Formation and locality—Rare near the base of the Trenton shales, near Fountain, Minnesota. .In
the original description the locality is given, inadvertently, as Minneapolis.

ARTHROSTYLUS oBLIQUUS Ulrich.
PLATE III, FIGS. 15 and 16.
Arthrostylus obliquus ULRICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 190.
Original description: “Zoarium jointed, segments very slender, needle-shaped,

straight or slightly curved, about 4 mm long, subquadrangular in cross-section, 0.2
mm wide, 0.15 mm. thick, slightly expanding toward the upper extremity. Zocecia
BRYOZOA. 189
Helopora.] :

in three rows, occupying as many faces of the segment, the fourth side with three
longitudinal striz, and no zoecia. Profile of a segment in an obverse or reverse
view, wavy on both sides; in a lateral view only on one side.

“Zocecial apertures small, oblique, the posterior margin very prominent, arranged
alternately in the three rows, with nine in each, in 2.5mm. A short ridge from the
upper depressed edge of each zocecial aperture is flanked on each side by the pro-
longed lateral borders of the aperture. No ridge between the lateral and central
row of the zocecia.

“The oblique zocecial apertures, the prominent lower border and absence of ridges
between the rows of apertures, distinguish this species from A. conjunctus and A.
tenuis, both of which it resembles in other respects.”

Formation and locality Trenton shales, Minneapolis, Minnesota; rare.

Genus HELOPORA, Hall.

Helopora, HALL, 1852, Pal. N. Y.. vol. ii, p. 44; BILLINes, 1866, (part.) Cata. Sil. Foss. Isl. Antic.,
p. 36; ULRICH, 1888, The Amer. Geologist, vol. i. No. 4, p. 231, 1890,
Jour. Cin, Soc. Nat. Hist., vol. xii, p. 191, and 1890, Geol. Surv. Ill.,
vol. viii, pp. 401 and 642,

Zoaria consisting of numerous, subequal, small, cylindrical segments, articulating
terminally, poriferous on all sides. Zocecial tubes somewhat oblique, geniculated or
proceeding to the surface in a straight line. Apertures slightly oblique or appearing
direct, suboval, arranged in diagonally intersecting series (section a) or between more
or less well defined longitudinal ridges (section 6). In section a the apertures are
usually without a peristome, but an acanthopore occurs immediately beneath each. In
section } the acanthopores are wanting, but a peristome, generally incomplete and
prominently elevated posteriorly, is present. Axial tube very slender.

Type: A. fragilis Hall, a common fossil of the Clinton group.

As is indicated above, this genus may be divided into two sections. These were
noted in my previous work on the genus (loc. cif.) andin one of them I express the
opinion that, when these fossils are better understood, these two sections will
probably be separated generically. Although the study of the genus, necessitated
by the present work, has strengthened this opinion, I am not yet ready to make
the separation. Still, I shall go a step farther here and follow the practice
adopted in treating many of the preceding genera. As in those cases I believe
this non-committal division of the species into sections will suffice until we are
in a position to work up the genus monographically. Except in that way it is
not only difficult but almost impossible to distinguish nearly related genera in a

fully satisfactory manner.
190 THE PALEONTOLOGY OF MINNESOTA.
[Helopora.

Section a embraces the species which agree nearest with the type of the genus,
and all of them, as far as known, belong to Upper Silurian rocks (including the
Anticosti group). They are distinguished from the species of section b (1) by the
presence of acanthopores, one of which is commonly situated in each end space ; (2)
the absence of longitudinal ridges and inter-apertural strie ; (8) the predominance of
the diagonal arrangement of the zocecial apertures; (4) the absence of a peristome,
the interspaces being highest midway below the zocecial apertures and sloping into
them, and (5) the lesser separation of the zocecial apertures longitudinally.

Under section a I would place H. fragilis Hall, from the Clinton of New York,
Canada, and probably Ohio; H. bellula, H. armata, and H. nodosa, three species
described by Billings from the Anticosti group, and H. lindstremi Ulrich, from the
Upper Silurian of the island of Gotland.

Section b differs from the typical section (1) by the absence of acanthopores; (2)
the presence of straight or wavy ridges and minor striations of the surface; (3) the
predominance of the longitudinal and transverse arrangement of the zocecial aper- -
tures; (4) the prominence of the zocecial apertures, especially at the inferior side,
and (5) in the more ornamental appearance’of the segments resulting from the pecu-
liarities noted.

Helopora spiniformis, originally described by me as Arthroclema spiniforme (Jour.
Cin. Soc. Nat. Hist., vol V, p. 161, 1882), may well be accepted as the type of this
section. This species is fairly abundant on slabs of “Glade ” limestones, at Lebanon,
LaVergne, and other localities in Tennessee. Figs. 4, 5 and 6, on plate III, intro-
duced chiefly for comparison with H. divaricata, illustrate its principal characters.
Segments of apparently the same species were collected also in the lower limestones
at Dixon, Illinois.

All the other known Lower Silurian species referred to the genus must be
arranged in section b. These are H. quadrata, n. sp., H. mucronata Ulrich, and H.(?)
sp. undet., from the Galena shales of Minnesota, the last two with rather striking
resemblances to certain Cylostomata; H. harrisi James, H. elegans, n. sp. and
H, imbricata Ulrich, from the upper beds of the Cincinnati group of Ohio and
Illinois; and H. alternata Ulrich, from the Trenton shales of Minnesota. The last
represents a peculiar type of the section that is again met with, but less strongly
expressed in the new species I. elegans. :

As is to be expected, it is in section b that Helopora most nearly approaches the
other genera of the family. The species of section a represent a further differenti-
ation of the type. Comparing the former with Arthroclema we note a general
agreement of structure, which, if we knew nothing of the segments of the primary
and secondary order of that genus, might really be said to amount to identity. But
Helopora.] BRYOZOA. 191

we do know that the zoarial combination of the segments in Arthroclema is by both
terminal and lateral articulation, while in Helopora they unite at their ends only.
The difficulties, therefore, which we may experience in correctly classifying some of
the dismembered segments, are not at all encountered when we deal with complete
zoaria. Even granting that the latter condition is exceedingly rare, the trouble of
discriminating between the isolated segments of the two genera is not of very com-
mon occurrence, because it is restricted to those of the third order of Arthroclema,
those of the primary and secondary set being easily distinguished from Helopora by
the lateral articular socket. In practice I think we are nearly safe under this work-
ing rule: When of a number of isolated segments occurring on slabs of rock or in
the residue of shale washings, none have lateral sockets, it is safe to classify them as
Helopora, providing, of course, that they agree with that genus in other respects.
When, however, one or more of them possess such sockets, it is to be recommended
that the investigator determine the three sets of segments of the Arthroclema before
he classifies any of them as Helopora.

Of the remaining genera of the family, Sceptropora is distinguished by i wide
expansion or swelling of the upper half of the segments; Arthrostylus in having one
side simply striated and without zoccial apertures, and Nematopora by its branch-
ing zoaria and the absence of joints above the basal articulation. The placing of
such species with Helopora, by Billings, was an error that I am convinced he would
not have committed had he known that Helopora originally consisted of numerous
subequal segments joined together into bushy zoaria.

Hetopora pivaricata Ulrich.
PLATE III, FIGS. 1-3.

' Helopora divaricata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 59.

Zoarium jointed ; segments about 7.0 mm. long, obtuse at both extremities, sub-
cylindrical, polygonal in cross-section, the number of the angles and corresponding
rows of zocecial apertures six, seven or eight. Their diameter varies with age and
according to the number of zocecia contained from 0.5 to 0.9mm. Zocecial apertures
comparatively large, oblique, ovate, seeming to widen anteriorly, arranged in troughs
‘between strong longitudinal ridges, twelve in 5 mm. lengthwise and generally in
regular transverse rows. Posterior border of apertures thick, prominent, sloping
backward into the aperture next below. This border is continued upon the sides of#
the zocecial aperture as two diverging ridges which extend on each side to the sum-
mit of the longitudinal keels where they meet with similar ridges from the adjoin-
ing rows. These divaricating ridges cause the strong vertical keels to appear as
192 THE PALEONTOLOGY OF MINNESOTA.
[Helopora.

being marked by a succession of narrow (-shaped furrows and ridges. Occasionally,
and this is true more especially of the young and slender segments, the rounded
posterior slope is divided by a central furrow into two small ridges, the same as in
H. spiniformis and H. mucronata.

Except the transverse section figured on plate III, the thin sections prepared of
this species are not satisfactory. As far as they go it appears that the internal
structure is not materially different from that of H. spiniformis, (see plate III, figs. 5
and 6) to which species it is closely related. In H. divaricata the zocecial apertures
are wider, as are also the troughs into which they open, whilst the vertical ridges
which separate the rows of zoccia are always a more pronounced feature than in
H. spiniformis. When segments of the two species having the same diameter are
compared, those of the latter species will be found to have at least one more row of
zocecia, and to be more nearly cylindrical. With age the angles become entirely
effaced, the zocecial apertures relatively smaller than shown in my figures, all the
interspaces nearly on a level, and the striation almost equal throughout. The lower
extremity of the segments of H. spiniformis also are always more pointed than in
H, divaricata.

Formation and locality.—Rather rare in the lower third of the Trenton shales, at Minneapolis, Min-
nesota.

Mus. Reg. No. 5928.

Hetopora aLTeRNatA Ulrich.
f
PLATE III, FIG. 9.

Helopora alternata Ulrich, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 192.

-

Segments exceedingly slender, slightly curved, about 5.0 mm. long, and scarcely
0.25 mm. in diameter; lower extremity obtusely pointed, the upper rounded. Zoc-
cial apertures oval, nearly direct, comparatively large, about 0.13 mm. in length,
arranged alternately, four in each cycle, twelve cycles in 2.5 mm., and twelve or
thirteen in a direct line 5mm. long. Interspaces rather thin, generally appearing
to be simply rounded, but, with the light coming from the side, two narrow furrows,
passing in a sinuous manner between the apertures, are to be seen. The result is thin
peristomes united longitudinally by a thin connecting ridge.

The exceeding delicacy of the segments and the ‘comparatively large size and
alternate arrangement of the zocecial apertures of this species causes it to be distin-
guished without difficulty from all known Trenton forms.

Formation and localityRare at the base of the middle third of the Trenton shales, Minneapolis,
Minnesota.
Helopora.]~ BRYOZOA. 193

HeLopora mucronata Ulrich.
PLATE III, FIG. 10.

Helopora mucronata Uxricn, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 192.

Segments spine-like, slightly curved, 3.5 to 4.0 mm. long, tapering downward from
the truncate upper end, where the diameter is 0.6 or 0.7 mm., to the acute and finely
striated basal extremity. Zocecial apertures oblique, the inferior and lateral margins
elevated, arranged longitudinally and spirally, with from six to eight forming a com-
plete volution, and six in about 2.5 mm. lengthwise. Above each zocecial aperture
two short striz. Obscure longitudinal ridges sometimes formed by the coalescence
and continuance of the elevated lateral margins of the zocecial apertures.

The curved and tapering form, the acute lower extremity, and the very slight
development of the longitudinal ridges, distinguish this species from all the associ-
ated jointed Bryozoa, as well as from H. divaricata and H. spiniformis. None of the
other species of the genus are sufficiently near to require comparisons.

Though readily distinguishable from all the known varieties of segments of the
associated Arthroclema armatum, it may yet be shown by complete zoaria of the latter
that H. mucronata is but another form of segment of Arthroclema. Until such evi-
dence is discovered we had best leave them as at present.

Formation and locality.—Galena shales, near Cannon Falls, Minnesota, where it is.associated with
Helopora quadrata, Arthroclema armatum, and several species of Nematopara. Also at St. Paul.

Mus. Reg. No. 8112.

HELOPORA QUADRATA, 2. Sp.

 

Fig. 10, Helopora quadrata ULRicu. Galena shales, near Cannon Falls, Minnesota. a, basal par
of a segment; b, the central portion of another, and c, the upper extremity of a third, all x 18.

Segments very slender, quadrate in cross-section, the angles sharp, the sides
each about 0.28 mm. wide; entire length unknown, none of the segments at hand
being complete, probably between 5 and 6 mm.; lower end bulbous, the upper with
two flattened articulating faces. Zocecial apertures in four longitudinal rows, one
on each of the concave sides ; ovate, a little oblique, the inferior and lateral margins
with a strong rim, produced backward, either straight or obliquely, as a sloping
ridge. Zocecial apertures separated by distances very nearly equal to their long

diameter, with nine or ten in 3 mm.
-13
194 THE PALEONTOLOGY OF MINNESOTA.

(el opora

This is the only species of the genus known to me having quadrate segments
and only four rows of zocecia. Fragments look a little like small, pieces of Nemato-
pora ovalis, an associated species, but are readily enough distinguished by their
sharper angles, and the relatively much greater elevation of the posterior margin of
their zocecial apertures.

The exceeding delicacy of the segments, and their structure in general, gives
them very much the appearance of species of Arthrostylus. But as all of the four
faces are occupied uniformily each by a row of zocecial apertures, it is evident that
the species does not belong to that genus.

Formation and locality.—Comparatively rare in washings of the Galena shales, near Cannon Falls,
Minnesota.

HELOPORA ELEGANS, 7. Sp. .

 

Fig. 11, Helopora: elegans ULRICH, Cincinnati group, Blanchester, Ohio. A segment of this species
of the natural size and x 18.

Segments small, subcylindrical, obtusely hexagonal in cross-sections, about 3.0
mm. long and 0.8 mm. in diameter; upper extremity truncate, the lower rounded and
tapering slightly. Zocecia in six longitudinal ranges, their apertures narrow-ellipti-
cal, slightly depressed in front, their length apart, arranged alternately in adjoining
rows. Entire surface beautifully grano-striate, the striz flexuous, forming con-
nected peristomes, with a short row of granules between the ends of the apertures
and a continuous row at each angle of the segment. The latter winds itself between
the zocecial apertures so as to arrange them into longitudinal series, with seven or
eight in the length of the segment.

Of all the species known to me H. alternata seems to be the nearest to this.
The differences between them are however too obvious to require pointing out.
H. harrisi occurs in the same beds, but its segments are longer and more slender, its
zocecia smaller, and the surface marking quite different.

Formation and locality.—The types are from the upper beds of the Cincinnati group, at Blanchester,
Ohio, but the species has been noticed at other localities in Ohio, and at Richmond and Versailles
in Indiana. I have also noticed similar segments in equivalent rocks at localities in Illinois, so that the
species may be expected to occur in these beds at localities in southern Minnesota.
Heendcad BRYOZOA. 198

HELOPoRA HARRISI James.
PLATE III, FIGS. 1, b,c, and 12.

Helopora harrisi Jams, 1883. “The Paleontologist,” p. 58.

Segments very small, acerate, about 3.5 mm. long, 0.22 mm. thick, hexagonal in
cross-section ; upper extremity slightly expanded, conical or pyramidal, with the
angles prominent, the lower end striated, tapering, obtusely pointed or slightly
bulbous ; between the ends the sides are nearly parallel. Zocecia in six longitudinal
ranges, their apertures small, narrow-elliptical, often drawn out anteriorly, their
margins thickened, about twice their length apart, with seven (usually) on each of
the six faces. Peristomes connected lengthwise, their sides being co-incident or
merged into the moderately developed ridges forming the angles of the segment.
The later are nearly always straight. Interspaces between the ends of the zoccial
apertures occupied by a low rounded ridge, rising and spreading at each end into
the peristomes. The best preserved examples exhibit a row of exceedingly minute
papille on the peristomes and angle-ridges.

In transverse sections the zocecia appear as six subequal wedge-shaped cells,
arranged around the central axis. The outer investment is rather thin, but in most
cases the projecting angles and the intermediate ridges are distinguishable. In
vertical sections the anterior side of the zoccia is nearly straight, forming an angle
of about fifty degrees with the axis. The zocecia are comparatively elongate, but the
overlap is unusually little. Sections on the whole are much like those of Nematopora
lineata Ulrich, as figured in Vol. viii, Ill. Geol. Sur., pl. X XIX, fiz. 7, but the zocecia
are more elongate in H. harris.

I cannot doubt that this is the species named by Mr. James in the publication
cited above, since the greater part of my specimens are from the same spot and
layer that furnished his types. But for this certainly I would not be able to identify
the species, Mr. James’ description being very incomplete and incorrect in some of
the points mentioned by him. I succeeded in obtaining free from the matrix fully
one thousand segments, and as many of these as have been examined show clearly
and uniformily six rows of cells, not two, three, or four as he supposed. He states
also that the sides are constricted at the ends of the apertures, “giving them a chain-
like appearance.” This is most certainly not true of any specimen seen by me. His
figures of the species too are as little or even less trustworthy. Indeed the two plates
which accompany that number of “The Paleontologist” may be said to burlesque

art illustration.*

*It is really a fair question whether a species so illy and insufficiently characterized as this, has any claim to
nition. In this case it happened that I had selected the same specific name for it, we having both intended to honor
Mn L H Harris of Waynesville, Ohio, who sent each of us one of the original specimens.
196 THE PALEONTOLOGY OF MINNESOTA.

{UWelopora.

The dismembered zoaria of this species literally made up a thin limestone
layer, 5 to 35 mm. thick, and about 2 meters square, which occurred in the soft
shales near Waynesville, Ohio. It is impossible to say how many segments may
have belonged to a single zoarium, but judging from their exceeding abundance
here it is more than probable that the number was often very large.

Formation and locality—Rather a characteristic fossil of the upper beds of the Cincinnati group.
The species is known from localities in Ohio, Indiana and Illinois, and has been found at Stony Mountain,
Manitoba.

Mus. Reg, No. 8113.

Hetopora (?) sp. undet.

PLATE III, FIG. 8.

Of this form my collection contains several segments that were found associated
with Helopora mucronata, H. quadrata and Arthroclena armatum. After careful
comparisons with those species, the last especially, I am obliged to regard them as
probably belonging to an undescribed species, which, because of the paucity of the
material at hand, I thought best to leave unnamed. A small one of what I believe
to be the tertiary or last set of segments of A. armatum is illustrated, beside one of
the supposed new species, on plate III by fig. 7. This is a little shorter than usual,
agreeing in that respect very nearly with the form under consideration, but in the
greater strength of its longitudinal ridges and in the character and number of the
zocecial apertures in a given space, it differs from the present species, while it agrees
in these features with the ordinary form of the third set of segments of A. arma-
tum. The segments in question are shorter than the average forms of either the
secondary or tertiary segments of A. armatum, and taking into consideration the
absence of a lateral socket, which should. be present in segments of this diameter, if
they belong to a species of Arthroclema, I think I am justified in maintaining, pro-
visionally, that they belong to a species of Helopora, with characters, briefly, as
follows :

Segments short, a little over 2 mm. in length, about 0.5 mm. in diameter, cylin-
drical, the upper extremity truncate, the lower tapering slightly but not pointed.
Zocecia in from eight to ten longitudinal rows, but the more obvious arrangement is
in five transverse or subspiral rows. Apertures subovate, oblique, widely separated
longitudinally, closely arranged transversely, the last fact, together with the pcom:
inence of the posterior border, giving the stems an annulated appearance. Delicate

ridges, which do not cross over the elevated margins of the zocecial apertures, define
their longitudinal arrangement.
BRYOZOA. 197

Arthroc’ema.]

Compared with species of Helopora, only two, H. spiniformis and H. mucronata,
require mention. Both have larger segments and the lower extremity more acute.
In the first the ridges and superficial striations are also more conspicuous, while in
the second the segments are curved and taper downward.

Formation and locality—Galena shales, near Cannon Falls, Minnesota.

Genus ARTHROCLEMA, Billings.

Arthroclema, BILLINGS, 1862, Pal. Foss., vol. i, p. 54; ULRIcH, 1886, Fourteenth Ann. Rep. Geol.
Nat. Hist. Sur. Minn., p. 60; 1888, The American Geologist, vol. i,
p. 232; 1890, Jour. Cin. Soc. Nat. Hist., vol. xii, p. 192, and Geol.
Sur. IIL, vol. viii, p. 400.

Arthroclema (part), ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 151.

Zoarium jointed, composed of numerous subcylindrical segments, celluliferous
on all sides, arranged in a pinnate manner; articulation both terminal and lateral.
Segments of three kinds, primary, secondary and tertiary. The first set forms the
strong central stem, of which each part has normally one or two sockets on opposite
sides for articulation with the smaller segments of the second set. The latter gen-
erally articulate in like manner, terminally with each other and laterally with the
still more slender segments of the third set. Zocecia subtubular, each occasionally
with a diaphragm, their apertures ovate, oblique, the inferior border more or less
prominent, arranged in rows between longitudinal ridges. Interspaces usually stri-
ated, often grano-striate.

Type: <A pulchellum Billings.

Complete zoaria are known of only two species of this genus, the type and
A, billingsi. This is unfortunate because of the difficulty of determining the range
of variation that may obtain in the three sets of segments. If the student will
examine fig. 7, on plate IL, he may appreciate the difficulties referred to. This
illustration represents the fine type specimen of A. billingsi, and gives a good idea of
the arrangement and the differences in the size and length of the segments of the
three sets that may occur in a species of Arthroclema. As shown in the figure the
segments of the same set even may not be of uniform length. In A. billingsi the
first of the secondary set is twice the length of those succeeding it. Then again it
shows that while some of the secondary segments may articulate laterally with one
of the tertiary set, many others may be without them. As all the zoarial parts
spread approximately in the same plane, the development of tertiary segments must
depend very largely upon the space available. In A. billingsi this was much less
than in the other species since it is the only one known in which the primary seg-
ments articulate with four (two on each side) secondary. joints. In all the other
198 THE PALEONTOLOGY OF -MINNESOTA.

(Artbroclema.

species there is only one on each side, so that their growth was less compact, and
the chances for tertiary segments better. Still, it is possible that the third set of
joints may not, in some species, have been developed at all. This seems to be true
of A. cornutum, since lateral sockets have not been observed on any of the numerous
secondary segments of that species seen.

Regarding the present work on the genus I regret that I have not been able to
do the species justice in the way of illustration. I have sought to figure them as
fully as the plates at my disposal admitted. But with so many conditions demand-
ing representation, I was often at a loss in selecting the specimens which would go
farthest in aiding the student to identify the species.

Respecting the distribution of the species, A. cornutum and A. striatum are known
as yet only from the middle third of the Trenton shales of Minnesota. The next
species is the A. pulchellum Billings, described from the Trenton limestones of Canada,
and with whick «m inclined to identify a number of segments found by me in the
upper division o. ‘le shales at St. Paul and Cannon Falls. A. billingst is from a simi-
lar (perhaps a litle lower) horizon at Ottawa, Canada. The detached segments of A.
armatum were abundant in washings of the Galena shales obtained from a locality
near Cannon Falls. The last species is the A. angulare, described in vol. viii, Ill. Geol.
Surv., from the upper beds at Wilmington, Ill. It occurs also at Stony Mountain in
Manitoba.

The relations of Arthroclema to Helopora have already been discussed in the
remarks on the latter gemus..

ARTHROCLEMA STRIATUM, n, Sp.

PLATE II, FIGS. 22 and 24, and PLATE III, FIGS, 28-33,

~

Under this name I propose to arrange a variety of segments that, though closely
related to A. pulchellum Billings, are evidently distinct. The specimens consist (1) of
a relatively small number of segments like the original of fig. 28; (2) hundreds like
figs. 22 and 23, and (3) equally numerous more slender segments. They agree with
each other in what I regard as specific characters, and in the following description
are referred to respectively as primary, secondary and tertiary segments.

Primary segments 2.5 to 3.0 mm. long, from 0.7 to 1.0 mm. in diameter in the
middle, spreading at the ends to a diameter of 1.2 mm. or more, the upper extremity
flat, generally subcircular, the lower also abrupt but rising centrally into an obtusely
conical elevation. Sometimes with only a single, large, deep and sharply defined
socket, situated very near the base; more commonly with two, placed on opposite
sides of the segment. Occasionally a third socket, this one small and illy defined, is
Arthroclema BRYOZOA. 199

placed near the upper end. Zocecia in five or six longitudinal rows, with small
oblique apertures, the posterior margin prominent; arranged in transverse rows,
with six the usual number in the length of the segment; short segments (2.5 mm.)
have five. Surface distinctly striated lengthwise, often thrown into strong, but
never sharp, ridges between which the zoccial apertures are arranged. The latter
are always difficult to see. In drawing fig. 30 I overlooked them entirely, having
mistaken certain depressions, which are often met with in these segments, for them.
Since freeing the specimen from the matrix I find that it has really five rows of
apertures, both longitudinally and transversely, of the same size as shown in fig. 33.
With this correction the figure may still be of aid in the identification of the species,
because it shows the striation of the surface better than the original of fig. 28. It
should be added, however, that the latter shows the usual shape of the segments
better. : \

Secondary ‘segments five-sided, 2.7 to 3.2 mm. long, the length depending upon
the number (six or seven) of transverse rows of zocecial apertures, 0.35 to 0.5 mm. in
diameter, the ends usually a little wider, the upper flat, the lower rounded. Zocecial
apertures in five longitudinal and six or seven transverse rows, small, oblique, drawn
out above, their ends widely separated. Interspaces finely striated lengthwise, the
angles sharp or rounded, formed by a raised central line and one or two similar lines
on each side of it. An articulating scar or shallow socket has been observed just

- above one of the first cycle of zocecial apertures, but their presence in the segments
of this set is to be counted as an unusual occurrence. For this reason it is more
than probable that most of the segments which are next described as tertiary are
really young or terminal joints of the second order.

Tertiary segments about 3.0 mm. long, less than 0.385 mm. in diameter, very
slender, four or five-sided, with sharp angles, the lower end rounded and tapering
slightly, the upper sharply truncate. Zocecia in four or five longitudinal rows, in
six, but oftener in seven cycles, their apertures small, oblique, the raised margin
highest, posteriorly and running out on each side to the angle ridges. Behind each

-/‘aperture usually a pair of very delicate striz, the conditions being very much as in
Helopora spiniformis (see plate IL, fig. 4). Angles formed by a single raised line.
These segments are distinguished from those of the second order by their/ greater
tenuity, more oblique zocecial apertures, and absence of striz on the sides of the
angle ridges. ; -

As stated in the paragraph preceding the last, it is possible that many of the
segments just described as of the tertiary set really represent the young stage of the
secondary set. In that case it is probable thav the four-sided joints only are ter-

tiaries.
200 THE PALEONTOLOGY OF MINNESOTA.

Arthroclema

This species is readily distinguished from its associate, A. cornutum, by its longer
and differently shaped segments, narrower zocecial apertures and simply striated
surface. It is closely allied to A. pulchellum Billings, but that species differs in hav-
ing the segments a trifle shorter (eight or nine in 20 mm.), the articulating sockets
situated near the middle instead of near the bottom of the joints, the primary seg-
ments less expanded at the ends, the zocecial apertures more direct, larger and sepa-
rated lengthwise by shorter interspaces.

Formation and locality.—The detached segments of this species are very plentiful on some of the
thin plates of limestone found in the lower part of the Trenton shales at Minneapolis and St. Paul,
Minnesota.

Mus. Reg. No. 8114.

‘

ARTHROCLEMA corNutTUM Ulrich.
PLATE IT, FIGS. 16-21 and 23.

Arthroclema cornutum Uxnricn, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 193.

Zoarium jointed, the segments five-sided, consisting possibly of three sets, but
only two are positively known. For the sake of convenient reference these will be
termed primary and secondary.

Primary segments five-sided,* about 2 mm. long, 0.5 to 0.7 mm. in diameter,
with the five angles more or less well-defined, though never sharp, produced at the
truncated and hollow upper extremity into as many horn-like projections. Near the
lower extremity, which is often a little bulbous and radially striated, there is usually
one rather shallow, subcircular articulating socket. It would appear that the
sockets were placed in these alternately on opposite sides of succeeding segments.
There may have been, as I believed, originally two sockets on some of the segments,
but no more than one is to be seen on any of those that have since been freed from
the matrix. Zocecia in five longitudinal rows, and generally in four, rarely in five,
cycles, the apertures of those in the uppermost cycle more oblique than the others
and situated very near the upper extremity of the yegment. Angles of segments,
peristomes of oval zocecial apertures, and the longitudinal interspaces more or less
regularly papillose. With age the number of rows of papilla at the angles increases
from one to three or four.

Secondary segments also five-sided, 0.4 to 0.5 mm. in diameter, from 1.0 to
1.8 mm. long, the usual length about 1.2 mm., with five in about 6.2mm. The length
depends upon the number of cycles of zocecial apertures. These are commonly only
three, but four cycles are not infrequent. Lateral articulating sockets apparently
wanting in this set. Otherwise very similar to the primary series. The papillose
ornamentation of the surface however is generally more regular, |

*In the original description I say “six-sided”, but this proves to be an error,
BRYOZOA. 201

Arthroclema.]

Compared with other species A. armatum, of the Galena shales, has larger and
much longer segments, six or seven rows of zocecia, and the lower border of their
apertures prominently produced. A. striatum, which is associated and more abun-
dant on the same slabs, differs in having longer and differently shaped seg-
ments, smaller zoccial apertures, generally six cycles of them, the surface striation
finer and without papilli, and in having the angles but little if at all produced at
the upper extremity. A. pulchellum Billings, differs in a similar manner.

Formation and locality—The detached segments of this species are rather plentiful on certain lay-
ers of the limestone plates in the lower part of the Trenton shales exposed in the railroad cut near the
State University at Minneapolis.

Mus. Reg. No. 8115.

ARTHROCLEMA ARMATUM Ulrich.
PLATE II, FIGS. 8-11, 25 and 28-33, and PLATEIII, FIG. 7.

Arthroclema armatum ULRicu, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 194, fig. 19, a, b, c, and,
d; note, f, g, h.*

Zoarium jointed, consisting of three sets of segments, primary, secondary and
tertiary, the first and second sets readily separable, the second and third probably
indistinguishable in many cases.

Primary segments generally subcylindrical, often compressed and irregularly
shaped, without regular longitudinal angles, the surface usually appearing as simply
striated, with strong spines and zocecial apertures indistinct ; length unusually vari-
able, depending upon the number of cycles of zocecia in the segment, 3.0 mm. with
seven cycles, 3.38 mm. with eight, 4.0 mm., the commonest size, with ten, and so on
to 4.5 mm.; diameter varying with age from 0.5 to 1.0 mm.; ends truncate, the upper
flat or raised centrally, the lower usually with a nipple-shaped prominence. Lateral
articulating sockets deep, sharply defined, situated at or slightly above the middle
of the length, so far as observed, never more than one to each segment; some are
without any. Zocecia in six ranges, their apertures oval, small, slightly oblique,
easily overlooked, sometimes, especially in the vicinity of the articulating socket,
closed, with seven in about 2.5 mm.; width of lateral interspaces varying with age.
A strong tubercle just behind or near each aperture.

Secondary segments of about the same length as the primary set, usually about
36mm. They are, however, more slender, none being more than 0.5 mm. in diame-
ter, ranging from that down to 0.3mm. Upper end terminating abruptly, spinous;
lower end rounded. Lateral sockets faint, centrally situated, not often detected in
this set. Zocecia rarely in five, commonly in six, occasionally in seven longitudinal

In the original work on this species one vertical section and three transverse sections of a Canadian example of
A. pulchellum BILLINGS, were inadvertently given as A.armatum. These figures which are magnified x 25 instead of x 18, are

reproduced in this volume on plate LL;
202 THE PALEONTOLOGY OF MINNESOTA.

[Arthroclema.

rows, arranged between prominent ridges that become stronger with age. A trans-
verse arrangement also prevails, with about seven in 2.5 mm.; according to its length
from seven to twelve cycles, the usual numbers nine or ten, are to be counted
in each segment. Apertures ovate, oblique, the inferior border very. prominent,
spine-like. With a favorable light, two exceedingly delicate strize may be noticed
in the longitudinal interspaces. These striz are not only generally present in
species of this genus, but also occur frequently in species of Helopora. They are not
shown in figs. 10 and 11, having been overlooked.

As tertiary segments I propose to denominate a large number that seem to belong
to this species but are more slender and differ in other respects from the ordinary
forms of the secondary set. As a rule, they have tapering, subequal, rounded extrem-
ities, are shorter, 2.5 to 3.8 mm. long, 0.3 mm. or less in diameter, five or six-sided,
the latter generally, with thé angles obscure in the youngest, but becoming fairly
prominent with age. At the same time the raised border of the zocecial apextures,
which at first is very thin, increases in strength and prominence. Six to eight
cycles of zocecial apertures in the length of a segment. Figure 7, on plate III,
represents an average segment of this set. In still younger specimens the angle
ridges are less conspicuous, while in going the other way an almost continuous
chain of variation from it to fig. 10 on plate II, can be selected from the material
before me.

This species is nearer A. pulchellum Billings, than I suspected at first. The only
differences that I now would insist on are (1) the greater average length of the seg-
ments, those of the second order especially, of the present species ; (2) the spine-like
elevation of the inferior border of the zocecial apertures, and (3) the less frequent
branching of the zoarium. In the Canadian species, of which I have some very good
material, the primary segments have almost invariably two lateral articulating
sockets, while the majority of those of the second order have one at least. In A.
armatum, however, the primaries have only one or none, and the secondaries are in
most cases without any. The two species of the lower shales, A. striatum and A.
cornutum, are readily enough distinguished. Both have the lateral articulating
sockets situated lower on the segments; the former has, furthermore, smaller
zocecial apertures, more numerous and finer surface striations and only five instead "
of six ranges of zocecia in the secondaries. The segments of A. cornutum are of a
different shape and much shorter.

If complete zoaria of this species could be studied, it would not surprise me if
they proved that the curved and taperingsegments which I have named Helopora
mucronata, and which are found in the same beds, are really parts of this Arthroclema.
BRYOZOA. 203

Arthroclema.]

Such a possibility may seem remote, yet its realization is rendered almost probable
by the recent discovery of similarly curved and pointed segments that belonged
unquestionably to the tertiary series of a small example of A. pulchellum.

Formation and locality.—Galena shales, near Cannon Falls, Minnesota, where it is associated with
many other small Bryozoa. Also in the upper shales at St. Paul, Minnesota.

Mus, Reg. No. 8116.

ARTHROCLEMA, sp. undet. (1).

°

PLATE II, FIGS. 26 and 27.

This species is represented in my cabinet by five segments collected from the
Trenton shales near Fountain, Minnesota. It may be distinct, but the material at
hand is insufficient for the foundation of a species of this genus. Figures 26 and 27
(plate II) represent the two offéring the greatest differences shown in the lot. One
is incomplete, having lost the two upper cycles of zoccia. It was evidently a
younger segment than the other, being less coarsley marked, with the angle ridges
straighter and more prominent. One of these segments shows a lateral scar situated
near the center, but it is very faintly impressed and easily overlooked. The zocecia
form six rows, but one segment seems to have had only five, with rather large,
obliqué apertures; aside from the incomplete segment (fig. 26) the transverse arrange-
ment of the apertures in the others is more or less irregularly spiral ; five apertures,
one at the extreme top, is the usual number in the segment length. Inter-apertural
spaces rather irregularly grano-striate. Length of segments about 2.4 mm., diameter
of same 0.35 to 0,4 mm.

The species to which these segments belong is probably a close ally of A. pul-
chellum Billings, on the one hand, and A. striatum on the other. These relations,
however, cannot be determined satisfactorily until more complete collections are

available.

ARTHROCLEMA, sp. undet. (2).

PLATE III, FIGS. 35-87.

Of this form, which is evidently related to the preceding and to A. pulchellum
Billings, but, so far as I can see, not identical with either, I have over twenty-five
more or less imperfect segments. These vary in length from 1.7 to 2.3 mm., and in
diameter from 0.3 to 0.5 mm. In several a faint, centrally situated, lateral socket is
distinguishable, and in most of them the zocecial apertures, of which there are four
or five cycles and six longitudinal rows, are inclined to be irregular in their arrange-
ment. A number of specimens are preserved as casts of the interior, and in these
(see plate III, figs. 36 rand 87) a spiral arrangement of the zowcia commonly pre-
204 : THE PALEONTOLOGY OF MINNESOTA.

[Nematopora.

vails. The surface is striated, especially on the more regularly constructed segments,
very much as in A, pulchellum. Though inclined to regard it as an illy nourished
variety of that species, with shorter and more slender segments, I- prefer, for the
present, to leave the form unclassified specifically.

All the specimens of this form were collected by me in the upper part of the
Trenton shales at St. Paul, Minnesota.

Genus NEMATOPORA, Ulrich. -

Nematopora, ULRIcu, 1888, The American Geologist, vol. i, p. 234; 1890, Illinois Geol. Surv., vol. viii,
pp. 401 and 644.

Zoaria very slender, branching, continuous above the pointed basal extremity.
Zoecia subtubular, short, arranged in a radial manner around one or two exceed-
ingly minute axial tubes. Apertures arranged in longitudinal series between smooth
or granulose ridges, nearly direct, generally elongate-ovate and enclosed by a thin
peristome. One or two diaphragms occasionally present.

Type: WN. ovalis Ulrich (N. quadrata Ulrich, Ill. Geol. Surv., vol, viii, 1890).

Of this genus we now know about fourteen species. Seven of these are from
Trenton rocks, one (undescribed) from the Cincinnati and Hudson River groups, five
from the Anticosti, and one, N. minuta Hall, sp., from the Niagara of Indiana.

The genus differs conspicuously from the other generic types included in the
Arthrostylide in having the zoarium continuous and dichotomously branched, the
jointed character prevailing in the family being confined to the basal extremity.
This part of the zoarium is, however, known of only one or two of the species, and
it may yet be proven that in some of the species there is no basal articulation. But
in the meantime, especially since the various forms agree very closely in zocecial
features, we may assume that the lower extremity was pointed and articulated with
a small basal expansion. The relations to Helopora, Hall, are therefore very nearly
the same as between Escharopora, Hall, and Arthropora, Ulrich.

Nemaropora ovauis Ulrich.
PLATE III, FIGS. 24 and 25.

Nematopora ovalis ULRICH, March, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 197.
Nematopora quadrata ULRicH, Dec., 1890. Ill. Geo. Surv., vol. viii, p. 644.

Original description: “Zoarium ramose; branches birfurcating at intervals of
about 2 mm., 0.3 to 0.4 mm. in diameter, subquadrangular or pentagonal in cross-
section, each face with a row of zocecia. Zocecial apertures direct, very large, oval,
nearly 0.3 mm. long by 0,15 mm, wide, enclosed by a sharply defined peristome, A
BRYOZOA. 205

Nematopora.]

short ridge joins the peristomes of each row of apertures, and longitudinally divides
the concave spaces between the ends of the apertures. These spaces are larger in
the subquadrate examples than in those having five rows of zocecia. They also have
the thin ridge that bounds each face more distinct from the elevated margins or
peristomes of the zocecial apertures, which, in the pentagonal specimens, to a large
extent also form the border of the faces. Longitudinal interspaces generally shorter
than the length of the zocecial apertures ; about five of the latter in 2.5 mm.”

Careful comparisons between the New York types of Nematopora quadrata (loc. cit.)
and the originals of N. ovalis have convinced me of their specific identity. My belief
that the latter had larger zocecia proved incorrect, and as many of them have also
the double ridges at the angles of the branches, which were regarded as the main
peculiarity of the former, nothing is left to distinguish them. It is to be admitted,
however, that none of the New York examples of the species so far seen have more
than four rows of zocecia. :

The large size of its zocecial apertures will distinguish N. ovalis from the three
species next described. WN. lineata Billings, sp., of the Anticosti group, is a larger
species with six or seven rows of zocecia.

Formation and locality.w—Galena shales, near Cannon Falls, Minnesota; Trenton limestone, Trenton
Falls, New York, and Montreal,Canada.

Mus. Reg. No. 8110.

Nematopora Granosa Ulrich.
PLATE III, FIGS. 17-20.

Nematopora granosa Uuricn, 1890. Jour. Cin. Soc. Nat. Hist, vol. xii, p. 196.

Original description: “Zoarium ramose; branches bifurcating at rather long
intervals, from 0.25 to 0,88 mm. in diameter, the smallest quadrangular in cross-
section and with only four rows of zocecia; those of the average size, pentagonal,
and with five rows of cells. Zocecial apertures small, narrow, about seven in each
range.in 2.5 mm., enclosed by a series of minute granules. Longitudinal interspaces
with a small number of similar granules. Rows of apertures separated by more or
less well-developed straight or slightly flexuous granulose ridges.”

The papillose ornamentation of the ridges and interspaces, and the narrowness
of the zoccial apertures of this species distinguish it from all the others having the
essential characters of Nematopora known to me. Under the microscope the general
appearance of the zoarium is strikingly different from that of . ovalis, with which
it is associated. Equally marked differences will be noted when it is compared with
N. delicatula and N. conferta, both of which likewise occur in the same beds.
Externally, N. granosa presents not a little resemblance to small species of Rhombo-
206 THE PALEONTOLOGY OF MINNESOTA.

LNematopora.

ora like R. lineinodis Ulrich, and R. regulars (Trematopora and later Orthopora regu-
laris Hall), but it is to be doubted that this resemblance is indicative of even remote
relation. In Rhombopora the primitive cells are drawn out into long tubes which
originate, just as they do in nearly all of the ramose T’repostomata, in various parts of
the axial region. In Nematopora, on the other hand, the zocecia are comparatively
short and arise along a definite axial line.

Formation and locality —Galena shales, near Cannon Falls, Minnesota.
Mus. Reg. No. 8111.

NeEMATOPORA DELICATULA Ulrich.
PLATE III, FIGS. 26 and 27.

Nematopora delicatula ULRICH, 1890. Geol. Sur. Ill., vol. viii, p. 646.

Zoarium very small and exceedingly slender, ramose above the pointed basal
extremity. Branches quadrangular, with the angles rather sharp, and the solid
sides flat or gently convex, each from 0.15 to 0.18 mm. wide. Zocecia rather long, in
four ranges ; apertures ovate or subcircular, about 0.12 mm. in length, separated by
long, smooth intervals, each from 0.7 to 1.0 mm. in length ; average length of zocecia
about 0.95 mm. Peristome thin, easily broken away; when perfect it forms a
sharply elevated rim about each aperture.

The widely separated zocecial apertures, and the exceeding delicacy and quad-
rangular form of the zoarium of this species distinguish it from all other species of
the genus known. The associated N. ovalis often has only four ranges of zocecia, but
their apertures are so much larger that the two species cannot be confounded. The
possibility of confusion with NV. granosa and N. conferta is equally remote. Indeed,
all of these four associated species are distinguished by sharply marked and easily
recognized peculiarities.

: ‘
Formation and locality.—Galena shales, near Cannon Falls, Minnesota. The original types of the
species were collected from an equivalent horizon in Alexander county, Illinois.*

Nematopora conrerta Ulrich.
PLATE ITI, FIGS. 21-23.

Nematopora conferta ULRIcH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 198.

Zoarium ramose, spreading nearly in a plane; branches dividing dichotomously
at intervals varying from 1 to 3 mm., 0.4 to 0.5 mm. in diameter, subcircular in cross-
section. Zocecia in five or six longitudinal ranges, their apertures frequently arranged

*In the Ill. Geol. Surv. vol. viii, this horizon is given, in conformity with the preceding volumes of publications of
that survey, as Cincinnati group, but at the top of p. 645 (op. cit.) it will be seen that I express a doubt as to their exact
age, saying that “I am inclined to regard them as more likely representing an upper member of the Trenton group.” I
have now satisfied myself that they are equivalent to the Galena of the Northwest and the Trenton limestone of New York,
:

BRYOZOA. 207
Phyloporinidz.]

also in rows encircling the stems. Apertures rounded or broad-oval, slightly oblique,
about 0.15 mm. in diameter, separated lengthwise by intervals a little greater than
their diameters, with seven or eight in 2.5 mm.; peristomes thin, strongest and
most elevated posteriorly. Interspaces striated, occasionally rising into strong ridges
which separated the longitudinal ranges of zocecial apertures for a short distance.

The smaller, subcircular apertures and differently marked interspaces, distin-
guish this species from N. ovalis. In N. granosa the zocecial apertures are much nar-
rower and alternately arranged, while the interspaces are papillose. WN. alternata
Ulrich, from a similar horizon in southern Illinois, has the zocecial apertures
arranged in quincunx, and differs in other obvious particulars.

Because of the rounded zocecial apertures and their prevailing mode of arrange-
ment, the branches of this species sometimes resemble those of Protocrisina exigua
Ulrich, a cyclostomatous:form that is associated with it at Cannon Falls. This
resemblance may prove a little troublesome when the surface of the Nematopora is
slightly abraded so that the striation of the interspaces is obscured. In all cases,
however, when the specimens can be observed free from the matrix they may be
distinguished at once by the fact that in the Nematopora the surface is celluliferous
on all sides, while in the Protocrisina one side of the branches is striated longitu-
dinally and without zocecial apertures.

Formation and locality.—Galena shales, near Cannon Falls, Minnesota, where it is associated with
the preceding species and many other small Bryozoa. Prasopora insularis Ulrich, is the commonest and
most characteristic fossil of this horizon.

Family PHYLLOPORINIDA, Ulrich.

The genera comprised in this family, Phylloporina, Drymotrypa and Chainodictyon,
are not very important in the way of specific and individual representation, but viewed
from a biologic standpoint they are decidedly interesting. This interest attaches
chiefly to the fact that they furnish excellent examples of what have been very aptly
termed “comprehensive types.”

A careful investigation of the internal structure of the various species of Phyllo-
porina leads us to the conviction that at some time prior to the age of the Chazy
there existed Bryozoa that combined characters which, during subsequent periods,
became separately specialized and characteristic of widely different groups of fami-
lies. Take, for instance, P. trentonensis Nicholson, sp., or P. sublaxa, P. halli and P.
corticosa of the present work. In all of these remarkable forms we are reminded
very strongly of typical Trepostomata, the subangular zocecial tubes, their long “im-
mature” region, diaphragms, mesopores and acanthopores being, all of them, char-

acteristic of species of that suborder.
208 THE PALEONTOLOGY OF MINNESOTA.
[Phylloporina.

On the other hand, in P. aspera Hall, P. reticulata Hall, P. dawsoni Ulrich, and P.
asperato-striata Hall, the zocecial tubes are shorter and thus approach the ordinary
cryptostomatous cell more nearly. Indeed, P. daisoni can be, I think, shown to be
the first recognizable stage in the line of development that later on resulted in the
highly diversified Fenestellidw. This same species, however, and the remark applies
with equal force to Drymotrypa dichotoma Ulrich, has much to remind us of Cyclosto-
mata like Protocrisina, the zocecial orifice being but little constricted and the enclos-
ing rim similarly prominent in all of them.

We can show, therefore, apparent relations to three suborders of Bryozoa, and it
becomes a question of some difficulty to decide where the family had best be placed.
The Cryptostomata, however, seem best adapted to receive them, chiefly for the rea-
son that the Phylloporinide and Fenestellide are doubtlessly derived from the same
stock, and the latter developed from the branch of the former mentioned.

Genus PHYLLOPORINA, Ulrich.

Retepora, as applied by various authors to Lower and Upper Silurian anastomosing Bryozoa (not
Lamarck, 1801).

Gorgonia ?, HALL, 1847, (not Gorgonia Linnaeus, 1745).

Intricaria, HALL, 1847; MILLER and Dygr, 1878, (not Defrance, 1823).

Phyllopora (part.), ULRicn, 1882. Jour. Cin. Soc. Nat Hist., vol. v, p. 150.

Nov. gen. (undesc.), ULRiIcH, 1886. Contri. to Amer. Pal., vol. i, No. 1, p. 5.

Phylloporina, ULRICH, 1890. Geol. Surv. Ill., vol. viii, pp. 399 and 639.

Zoaria retiform, consisting of somewhat irregularly anastomosing, slender
branches, with from two to eight ranges of zocecia on the obverse side. Reverse
convex, longitudinally striated, without apertures. Zocecia tubular, often with the
immature region very long, commonly with diaphragms. Apertures simple, uncon-
stricted, rounded or subangular, generally with a peristome. Mesopores present,
sometimes numerous, always closed at the surface; with diaphragms. Acan-
thopores often present.

Type: P. trentonensis (Retepora trentonensis Nicholson,* compare Retepora fene-
strata Hall}).

This genus includes some of the earliest types of Bryozoa known. Beginning in
the Chazy with three closely related species, the genus continues in the Birdseye
and Trenton with six or seven well-marked forms, four of which are described in the
following pages. In the Cincinnati group we have two species, in the Clinton one,
and in the Niagara one. The genus is not known from later deposits.

The affinities and natural relations of the genus have already been touched

upon in discussing the family. There remains to compare with Retepora, Imperato,

*Geological Mag., vol. 2, p. 387, 1875. i
+Third Report N. Y. St. Mus. Nat. Hist., p. 178, 1850.

 
Phylloporina.} BRYOZOA. 209

and Phyllopora, King, two genera that previous to 1888 were commonly employed in

designating species of Phylloporina. The three genera agree in having similarly

anastomosing zoaria, but the first belongs unquestionably tv the Chilostomata, and is

not known in rocks earlier than the Cretaceous. In the second the zoaria are short

and constructed in every respect like those which characterize the Fenestellide.

Phyllopora was not derived from the Lower Silurian Phylloporina, but from some

type of Polypora subsequent to the extinction of the Silurian forms. YetI am much.
inclined to believe that all three genera were derived successively from the same

primal stock—not from each other—and that we have here merely a case illustrating

the “tendency to variation in certain directions.”

Compared with Drymotrypa, Ulrich, a genus beginning in the Trenton, and con-
tinuing to the Lower Helderberg, the present genus is distinguished chiefly, perhaps
solely, by the anastomosis of the branches, these being dichotomously branched and
free in Drymotrypa. In the Carboniferous genus Chainodictyon, Foerste, the zocecia
are somewhat shorter, and the back or “ reverse ” flatter and marked concentrically
instead of longitudinally.

~ PHyLioporina suBLaxa Ulrich.
PLATE IV, FIGS. 1-7.

Phylloporina sublaxa Uunica, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 179.

Zoarium an undulating flabelliform expansion, attaining a diameter of 5 cm. or
more, consisting of irregularly inosculating slender subcylindrical branches, varying
in width from 0.8 to 0.6 mm., but averaging about 0.45 mm. Fenestrules large, sub-
acutely elliptical, varying considerably in shape and size, generally two or three
times longer than wide; measuring, longitudinally, the average number in 1 cm. is.
between five and six; transversely, nine or ten in the same space. These measure-

‘ments apply to the Tennessee specimens. In the Minnesota form of this species the
fenestrules are smaller, averaging between six and seven in | cm. lengthwise.

. Reverse of the Tennessee specimens strongly rounded, nearly smooth, or with faint
longitudinal Sie In very young examples the latter would probably be more
distinct. Figure 2 on plate IV represents an enlargement of the reverse of a small
fragment obtained from the lower part of the limestone at Minneapolis, Minnesota,
by splitting a block of limestone. As usual under such conditions the outer layer of
sclerenchyma has adhered to the opposite side of the matrix and exposed a more
youthful stage in the development of the zoarium, in which the reverse side was

strongly striated.
-14
210 ‘ -THE PALEONTOLOGY OF MINNESOTA. ‘
[Phylloporina reticulata

Obverse face of branches strongly convex, carrying three to five rows of zocecial
apertures. These are subcircular, with a scarcely appreciable peristome, 0.09 mm.
in diameter, and twenty-three to twenty-five in 5 mm. in each rdw, Interspaces
depressed, generally forming distinct pits between the ends of the cells. Sometimes
obscure raised lines may be detected between the rows of apertures. Acanthopores
small, usually abundant, with no definite arrangement. .

Thin sections show that the tubular primitive portion of the zocecia, which is
long and prismatic, is often intersected by from one to three diaphragms. Just
before bending outward to open at the surface the tubes become rounded, leaving
irregularly shaped interspaces or shallow mesopores. It is here also that the acan-
thopores are developed.

In.some respects this species occupies an intermediate position between P. tren-
tonensis Nicholson, sp., and P. granistriata Ulrich, both of which occur in higher beds
of the Trenton, proper. The first is more robust, with stronger branches, more
numerous rows of zocecia, and the primitive portion of the zowcia longer and
straighter. The zocecial apertures are also more angular. The second has more.
rigid branches, longer and narrower fenestrules, and the reverse side of the branches
grano-striate and on the whole more delicately marked. The fenestrules of P. reti-
culata Hall, sp., are so much smaller that even very small fragments may be dis-
tinguished at once.

; Formation and locality.—The Tennessee type specimens are from the Glade limestone at Lebanon
and La Vergne. Fragments of probably the same species occur in the ‘* Piercelimestone” at Murfreesboro.
The Minnesota examples were obtained from the lower part of the limestone at Minneapolis.

Mus. Reg. No. 5954.

PHYLLOPORINA RETICULATA Hall.
PLATE IV, FIGS. 8—15.

Intricaria reticulata HALL, 1847. Pal. N. Y., vol. i, p. 17.
Phylloporina reticulata ULRICH, 1890. Ill. Geol. Surv., vol. viii, pl. LIII, figs. 2, 2a.

Specimens as seen, consisting of small, flat or undulating, reticulate expansions,
being in each case evidently fragments of a depressed, funnel-shaped zoarium, prob-
ably not exceeding 5 cm. in diameter. Branches rounded in section, 0.2 to 0:3 mm.
in diameter, inosculating at unusually frequent and regular intervals. Fenestrules
somewhat elongate, about as wide as the branches, subrhomboidal in shape in the
more regularly constructed fragments ; their number in a given space is fairly con-
stant, the extremes noticed in 1 cm. being ten and twelve, Reverse of branches con-
vex, finely striated lengthwise, |
Phylloporina halli.] BRYOZOA. 21 ]

Obverse strongly convex, with three rather irregular rows of zoccia, their
apertures subcircular, with a distinct peristome, about 0.1 mm. in diameter, eight
or nine in 2 mm. Acanthopores abundant, irregularly distributed, rather large,
especially so in the earliest forms of the species. Interspaces slightly concave,
occasionally faintly pitted and striated. .

In tangential sections the zocecia are rather short, with a row on each side
directed obliquely outward, and one series between-them. The latter are wedge-
shaped, and in deep sections appear as a more or less narrow central space. Dia-
phragms, one in each tube, have been observed.

None of the other Minnesota species of the genus are closely related. All of
them are larger and stronger in both the branches and fenestrules. Nor are any of
them found in the same beds with P. reticulata.

Formation and locality.—Both the geological and geographical distribution of this species is
extended. It was described originally from the Trenton limestone of New York, and in that position
occurs also at many localities in Canada and Vermont, and at one or two points near Cannon Falls in
Minnesota. In this state, however, a form occurs in the lower and middle thirds of the Trenton (Birdseye)
shales at Minneapolis and St. Paul, that is indistinguishable. As yet it has not been found in the upper
third of the shales, but, as stated, it reappears in the Galena shales (typical Trenton) near Cannon Falls,
It is not improbable that P. clathrata (Intricaria clathrata Miller and Dyer), of the Cincinnati group of
Ohio and Kentucky, is not specifically distinct from P. reticulata. At any rate I have so far failed to
detect sufficient points of difference.

Mus. Reg. No. 5955.

«

PuHyyioporina HALLI Ulrich.
PLATE IV, FIGS. 16-21.

Phylloporina hallé UbLRicH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 181.

Original description: “Zoarium an undulating foliate expansion of unknown
dimensions; the largest fragment seen is 3.5 cm. in diameter ; thickness of strongest
varying between 1.5 and 2.0 mm. Branches scarcely distinguishable as such, the
zoarium having the appearance of a perforated plate rather than consisting of inos-
culating branches.

“Peverse with the fenestrules small, subcircular or oval, arranged more or less
regularly in longitudinal and diagonal series, with from eight to ten in 1 cm. either
way. When the arrangement is regular they are approximately of the same size, but
when that is not the case some may be much smaller than the average. The latter
are about 0.4 mm. in diameter. Over portions of old examples there may be a
secondary deposit of sclerenchyma which occasionally fills the fenestrules com-
pletely. Such deposits are, however, much less frequent than upon the celluliferous

face. Branches convex, smooth, with an average width of 0.65 mm, Occasionally

one may be swollen to twice that,width.

’
212 THE PALEONTOLOGY OF MINNESOTA. .

[Phyloporina corticosa.

“Obverse generally presenting a very irregular appearance. This is largely due
to irregular, noncelluliferous deposits of sclerenchyma that occur at variable inter-
vals. The fenestrules, however, also seem less regularly arranged than upon the
reverse face. Surface of branches strongly convex, carrying from three to six or
more rows of alternating and scarcely circular zoccial apertures. These are about
0.09 mm. in diameter, without peristomes, and separated by intervals of less width
generally than their diameter. Some of the interspaces are a little prominent.
These may.have contained acanthopores. Five or six cell apertures in 1 mm.

“Although the preservation of the material is not the best for microscopical
determination of internal characters, thin sections still bring to light the more
salient features. They show thut the zoccial tubes are intersected by numerous
diaphragms ; that near their apertures they are still prismatic, resembling the zocecia
of a Monticuliporoid, and that a few small cells, perhaps acanthopores, are scattered
among the true zocecia.

“This is an easily recognized species, being also quite distinct from all the
others of the genus known. In its proportions it is somewhat like P. corticosa, from
the same horizon, but they are not likely to be confounded, the strong carinz on
both sides of the branches in that species serving amply in distinguishing them.”

Formation and locality.—Rather rare in the upper third of the Trenton shales, at St. Paul, Minnesota.

PHYLLOPORINA corTIcosa Ulrich.
PLATE V, FIGS. 1-10.
Phyllopora ? corticosa ULRICH, 1886. Fourteenth Ann. Rep. Geol. and Nat. Hist. Surv. of Minn,, p. 61.

Zoarium reticulate, arising from an expanded base, at first funnel-shaped and
poriferous on the outer side, later on becoming irregularly undulating. Poriferous
side presenting the appearance of a Fenestella or Semicoscinium with strongly
carinate and more or less flexuous anastomosing branches, and much depressed
dissepiments. Width of branches varying from 0.35 mm. to 0.9 mm., but averaging
about 0.5 or 0.6 mm.; thickness of branches and frond varying between 1.0 and 1.6 mm.

Obverse : On each side of the sharp, and, apparently, spiniferous median ridge,
there are rarely one, usually two, rows of irregularly alternating, circular peri-
stomate zocecial apertures, with nine or ten in eachin 2mm. Asa rule, the dissepi-
ment-like connections between the branches are short, depressed, and may or may
not carry a small number of zocecial apertures distinct from the series belonging to
the branches. Occasonally this division of the frond into rigid or flexuous branches
and depressed dissepiment-like connections is not recognizable on all parts of the
Phyloporina corticosa.] BRYOZOA. 213

fronds. In such cases the branches anastomose rather irregularly and are simply
convex, not carinate, the median ridge being absent. Fenestrules small, irregular,
narrow, often indented by the projecting zocecial apertures.

Reverse of branches very finely striated, tending, though less strongly than on
the obverse face, to form median longitudinal ridges. Fenestrules varying in out-
line from elongate-elliptical to subcircular, their width rarely more, usually a little
less than that of the branches, their length from one to three times the width ;
measuring transversely, six or seven in 5 mm.; longitudinally, the average number
in the same space is three.

Tangential sections, cutting the frond parallel with the plane of its expansion
and near the middle of its thickness, show that the branches are generally divided
into approximate halves by an obscurely double vertical lamina, thicker than the
walls of the zocecial tubes diverging slowly from it toward each side. The tubes
have thin walls, are long, and crossed by straight lines representing diaphragms.
The number of the latter depends upon age. Where the section divides the tubes
just beneath their apertures they are rounded or subangular, with slightly thickened
walls, partially separated from each other by solidly filled interspaces or mesopores,
that may be considerably smaller or even a little larger than the true zocecia. Here
and there, along the middle of the branches, a small acanthopore may be detected.

Vertical sections show that*the zocecial tubes arise also from a thick, laminated,
basal layer, from which they diverge in an upward and outward direction. Their
course toward the surface is very gradual in the lower half of the branch, but in the
upper half the curve is slightly accelerated so that their apertures are nearly direct
at the surface. Several diaphragms occur in the prostrate or primitive portion of
each tube and in young examples (plate V, fig. 10) they may be absent in the more
erect superficial portion. With age, however, additional diaphragms, now the
diameter of a tube distant from each other, are introduced. Near the surface the
tubes separate, leaving obconical interspaces, which are subsequently filled with
solid or laminated tissue.

In transverse sections the branches are subrhomboidal, the lateral diameter
being the shortest. The median ridge is shown to be an extension of the double
vertical wall already mentioned. Between the two lamine forming this wall, a
series of very minute tubuli, similar to those found between the median laminz of
many bifoliate Bryozoa, may be observed. On each side of this mesial wall the
zocecial tubes are piled over each other, in one or two series, three or four high.
These and other characters are well shown in fig. 9 on plate V.

This is a very remarkable species, and probably the most “comprehensive”
type known to me among the Bryozoa. That its place is with Phylloporina will,
214 THE PALEONTOLOGY OF MINNESOTA.
(Trepostomata.

I believe, be recognized at once, since it embraces every essential character of the
genus. But it has others that are not possessed by any of the other species. Chief
among these is the mesial ridge of the branches that brings to mind Semicoscinium
and Fenestralia of the. Fenestellide. As shown, this ridge is the superficial extension
of a double median lamina constructed upon the same plan as in the Rhinidictyonide.
Of course there is a difference in this that in the ordinary bifoliate Bryozoa the
median lamina is horizontal while in the P. corticosa it is vertical to the plane
of expansion. We find however precisely the latter condition in Goniocladia,
Ethridge, jun., a Carboniferous genus with relations to the Cystodictyonide, and in
Reticulipora, d’Orbigny, a Cretaceous genus of the Cyclostomata. If we add to these
peculiarities the general resemblance of the zoccial tubes of Phylloporina to those of
ordinary T'repostomata, and the common possession of mesopores and acanthopores,
we are confronted in P. corticosa by, to say the least, an unexpected mixture of
characters. These facts are not mentioned because they are believed to indicate
true relationships among the diverse types enumerated. On the contrary, it is
more than doubtful that any two of them belong to the same line of development.
Still, there is more than mere coincidence in the combination of characters seen in
P. corticosa, and in the genealogical studies that will be in order sooner or later,
they should be borne in mind.

Formation and locality.—Upper third of the Trenton shales, near Oxford Mills, Goodhue county,
Minnesota, where it is abundant. A few specimens have been found also at St. Paul, in equivalent beds.

Mus. Reg. No. 3495.

Suborder TREPOSTOMATA, Ulrich.

In nearly every respect this suborder is to be considered pre-eminent among the
Bryozoa of the Lower Silurian rocks ; and this is as true of those in the lower horizons
of the system as developed in Minnesota, as it is of those that have been so long
known in the Cincinnati rocks. As was stated in the introduction, the lower beds
holding Bryozoa in Minnesota are really very near the apparent inception of the
class, the oldest forms known being from the Chazy. This fact should not be forgot-
ten when the characters of the species and genera seem unstable and troublesome to
classify. That is to be expected, because, near their point of origin all classes of ani-
mals sufficiently studied may be shown to have been unsteady in their development,
new features having been introduced or dropped with surprising rapidity and fre-
quency. Some of these, at first wavering characters, later on, when the class became
fully established, assamed fundamental importance.
BRYOZOA. 915

Trepostomata.]

In the Minnesota shales, the minor or generic types of structure especially were
as yet most unstable, and the mixture that resulted in consequence is sometimes so
great and perplexing that it is perhaps impossible to do full justice to the affinities
of many species by any known practical method of classification.

The nearest approach probably to this desirable end is to be attained by the strictly
genealogical system of classification, which I may confess I am more than inclined
to adopt fully. The intricacy of this comparatively new and little understood system
seems to be the chief bar to its early and complete acceptance by naturalists. And
yet, so far as my experience goes, there is nothing very simple in the ramifications
of organic differentiation. On the contrary, forms are so intertwined in their rela-
tions that'to unravel them is a matter of the utmost difficulty and patient inquiry.
One of the more common of these difficulties is when we find a number of forms
agreeing apparently closely in all characters assumed to be generic, and of which
we have traced out the derivation of each so that we know them to have originated
in different stocks or lines of development. Among many cases of this kind, that of
Homotrypella ? ovata may serve as an example. This species has all the essential
characters of Homotrypella, and yet I believe I can show conclusively that it repre-
sents a departure from a line that originated in Homotrypa and later on, indeed soon,
developed into the Eridotrypa mutabilis Ulrich, group of species.

We know other species as well that stand in similarly equivocal relationship to
Homotrypa. A careful study of these brings us to two conclusions: (1) Homotrypa
generally manifested an inherent tendency to variation in that direction (7. e. to
develop mesopores), and (2) that such forms as Homotrypa similis Foord, are to be
regarded as reversions from the line of Homotrypa-Eridotrypa. Some of the questions
involved would be more easily answered were it not for the almost contemporaneous
existence of the variously differentiating types.*

*My studies have served in a number dt instances to throw light upon several as yet little developed thoughts in
evolution. Chief among these is the one occasionally referred to by me as a “Tendency to variation in certain direc-
tions.” This expression may sound simple enough, but the conditions expressed, providing they have been read aright,
are really of great importance in the classification of animal nature. Of course I cannot here enter into a full discussion
of the theory, but’a few ideas and facts pearing upon it seem desirable.

As results of presumed ‘“tendencies”’ we find conditions that may be expressed as follows: After a species has once
thrown off varieties of certain kinds, and these have died out, you may expect similar variations from continued decend-
ants of the type or species. Uases: (1) Dekayella prenuntia and varieties, and corresponding D. ulrichi and varieties (see
remarks under description of Dekayella); (2) the lower and middle Trenton species of Callopora, ampla, pulchelia, persimilis
and dumalis, described on succeeding pages, corresponding respectively to species subplana, dalet and ramosa, and an
undeseribed species, of the Cincinnati rocks; (3) the Lower Helderberg and Devonian species now classed as Thamniscus,
though derived, like the more typical Carboniferous and Permian species of that genus, from Polypora, are not the direct
ancestors of the latter, the first set of species having died out before the second were evolved; (4) Fenestella exhibited a
continual tendency to throw off varieties and species that gradually assumed the characteristics of Polypora. Many other
cases might be cited, but if those mentioned are followed up by the student I have no doubt he will find enough to con-
vinee himself that tendencies in variation, or evolution were preserved dormant under retrogression, but manifested
quickly enough when the proper conditions were presented. May not this idea explain the peculiar reapparition of
cyclostomatous types discussed on pp. 121 and 122? p ; . : :

Two other thoughts have suggested themselves in this connection. The first is that varieties and species were in
some instances reabsorbed into the parent stem. The other relates to an approximation in structure (1) by contemporaneous
forms or species that have had a common origin (¢é. g. Callopora undulata, Cc. incontroversa, Cc. angularis and C. ampla, all vary-
ing toward C. multitabulata), and (2) by forms known to have been derived through different lines of development gradually

assuming similar characters. as in the case of Homotrypa minnesotensis-Homotrypella ? ovata above described.
216 THE PALEONTOLOGY OF MINNESOTA.
LMonticuliporidz.

On plate XIX the figures up to No. 19 give an idea of the beginning of the line
of development referred to in the latter part of the paragraph preceding the last. In
Homotrypa minnesotensis we have what must still be regarded as a true species of the
geuus.* Even here, as shown in fig. 8, a tendency to interpolate mesopore-like
interspaces is occasionally manifest. In H. exilis this tendency is more strikingly
expressed and permanent, (see figs 13-16), while in H. separata it has progressed to
such an extent that the zocecia are rounded in shape instead of angular. These
three forms all occur in the lower third of the Trenton shales. In the middle third
we find a fourth stage in the development toward the Galena shales species provis-
ionally called Homotrypella ovata. This fourth stage has been named Homotrypa (?)
intercalaris and, as may be seen from the cut on a succeeding page, its characters are
very nearly intermediate between those of the species separata and ovata.

Difficulties like these were encountered all through my work on the Minnesota
Bryozoa, and now as it nears completion I realize, probably better than any one else
can, that the result, despite my utmost efforts, is not final nor even entirely satis-
factory in some parts. Had I followed my inclination and adopted a genealogical
arrangement throughout it might have been better, because I believe it would have
proven more permanent. But the criticism sometimes made that individual peculi-
arities are magnified into specific, and specific into generic, seemed to indicate a state
of knowledge not sufficiently advanced for the proper appreciation of all the innova-
tions that it would have been necessary to enter into. Perhaps I ought not to have
noticed criticisms which, like these, originate in ignorance of the fact that characters
preserved in hundreds of specimens are not to be viewed as “individual.” But I
have done so, and now must hope that the use of the interrogation point in cases of
the kind discussed may be deemed sufficient for immediate needs.

To prohibit repetition as much as possible I shall, in the course of the following
pages, frequently refer the student to the preceding paragraphs. |

Family MONTICULIPORIDA, Nicholson, emend. Ulrich.

This family is strongly represented in the Lower Silurian rocks of Minnesota, there
being here one or more species of every genus included in the family except Perono-
pora, Nicholson. The individuals of the species too are generally abundant, especially

those of Prasopora and Homotrypa, so that they constitute no inconsiderable part of
the collections from the various horizons.

*H, subramvsa, illustrated on the same plate, is more nearly like the prevailing Hudson River group types of the
genus.
Modtauitiees BRYOZOA. 217

The principal and almost infalliable distinguishing peculiarity of the family is
the cystiphragm. As a rule these structures form continuous series in the zocecial
tubes, and in all such cases their nature is at once determinable in either vertical
or tangential thin sections. But in the genera Monticulipora and Mesotrypa they are
often modified so that they might be mistaken for simple, oblique or slightly curved
diaphragms. On plate XV figures 8 and 9 illustrate the latter, while of the usual
form of the cystiphragms many examples are figured on plates XV to XIX.

Genus MONTICULIPORA, d’Orbigny.

' Monticulipora, d’ORBIGNY, 1850. Prodr. de Paleont., t. i, p..25.
Monticulipora (part.), NicHOLSoN, 1879. Struct. and Affin. of the Pal. Tabulate Corals, p. 269.
Peronopora (part.), NICHOLSON, 1881. ‘The Genus Monticulipora,” p. 215.
Monticulipora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, pp. 153 and 232; 1890, Geol. Surv. II1.,
vol. viii, pp. 370 and 407.

Zoarium massive, lobate, subramose, laminar, incrusting, or frondescent. Sur-
face usually tuberculated, sometimes even. Monticules closely arranged, usually
conical, often elongated or compressed. Zocecia polygonal, generally rather small,
with thin and, internally, peculiarly granulose walls. Mesopores few, generally
‘absent entirely. Cystiphragms present in the zocwcial tubes, both in the axial and
peripheral regions of the zoarium, usually in continuous series, but often isolated.
Acanthopores small, more or less numerous.

Type: M. mammulata d’Orbigny.

As now restricted this genus embraces but a small part of the incongruous ma-
terial for which the genus was a receptacle from the day it was established. Still,
no less than eighteen species having the essential characters of M. mammulata, all
of them Lower Silurian save one, are known to me. The earliest of these is from
the Birdseye limestone, and several belong to the Trenton proper; but it is in the
Hudson River rocks that the genus has its strongest development. So far the genus
is not known in Upper Silurian deposits, and it is possible that all its species became
extinct at the close of the Lower Silurian. If that should prove to be true the M.
winchelli Ulrich, described from the Hamilton of Michigan, could not be retained as
a true member of the genus, since its line of development would necessarily be

different.
218 THE PALEONTOLOGY OF MINNESOTA.
[Monticulipora wetherbyi.

. MoNTICULIPORA WETHERBYI Ulyich.
PLATE XV, FIGS. 7 and 8.

Monticulipora wetherbyi ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 239, pl. X, figs. 4-4b; 1889,
Contri. to the Micro-Paleon, of the Cambro-Silurian Rocks of Canada,
pt. ii, p. 30.

Zoarium attached to foreign objects, forming thin crusts or small depressed-
conical masses. Surface gently monticulose, sometimes nearly even. Zocecia
polygonal, with very thin walls, the diameter of those of the ordinary size about
0.25 mm. Clusters of larger cells attaining a diameter of from 0.3 to 0.38 mm.
occupy the summits and slopes of the monticules, or in the smooth forms are
scattered over the surface at intervals of about 2.5 mm., measuring from center
to center. A few small cells (? mesopores) may be detected, especially at the center
of the monticules, but they are always an inconspicuous feature and being of various
sizes are probably to be regarded as merely young zocecia. Acanthopores rather
large and numerous in tlie original Kentucky types of the species, small and few in
the northwestern form.

In longitudinal sections the zocecial tubes have thin walls with the granulose
structure characteristic of the genus. The transverse partitions, occurring at inter-
vals of a tube-diameter or more in the lower half of the tubes and little more than
a third of that distance apart near the surface, seem really to be all of the nature of
cystiphragms, though frequently appearing in the sections as straight diaphragms.
‘In transverse sections the tubes are angular and thin-walled, with strong acantho-
pores—one at most of the angles—in the Kentucky specimens, and much smaller
and fewer ones in the Minnesota and Manitoba form of the species. The cystoid
nature of the diaphragms is generally recognizable in these sections, but the cresentic
line, which is the unfailing mark of these structures, may not be detected except in
only a few of the zocecia. ;

Formation and locality.—Rare in the Birdseye limestone of central Kentucky. A single example was
found in the lower limestone at Minneapolis. ‘The species also occurs at St. Andrews, Manitoba.

Mus. Reg. No. 5967.
BRYOZOA. 219

Monticulipora incompta.]

MonricuLIPORA INCOMPTA, 7. sp.

PLATE XV, FIGS, 9-12.

Zoarium parasitic, forming inconsiderable crusts or small masses upon shells, 1 or
2 cm. in diameter and several mm. thick. Surface even, with inconspicuous clusters
of cells of slightly larger size than the average. Zocecia polygonal, with thin walls
(comparatively thick for the genus), the ordinary size varying between 0.2 and 0.25
mm, in diameter, while those in the clusters mentioned do not exceed 0.32 mm.,;
about eight in 2mm. True mesopores wanting, the small cells being shown by thin
sections to be merely young zocecia. Acanthopores small, inconspicuous externally.

The internal structure is so well illustrated on plate XV that-a detailed descrip-
tion is rendered superfluous. The chief peculiarity of the species'is the minutely
cellulose and roughish character of the zoccial walls. In all other respects the
species agrees closely enough with M. wetherbyi and M. lamellosa Ulrich, the latter
from the Hudson River rocks of Illinois.

Formation and locality.—Rather rare.in the middle third of the Trenton shales, at Minneapolis,
Minnesota.

Mus. Reg. No. 5968.

Monricutipora Graypis Ulrich.
PLATE XV, FIGS. 1-6.

Monticulipora grandis ULRICH, 1886. Fourteenth Ann. Rep. Geol. and Nat. Hist. Surv. Minn., p.78.

Zoarium irregularly massive, often tending to become lobate or subramose’
Zocecia polygonal, with thin walls. Surface without monticules, but exhibiting at
intervals of about 5 mm. conspicuous groups of cells larger than the average ; of the
latter nine or ten occur in 3 mm, while some of those in the clusters have been
observed to reach a diameter of 0.5 mm. No mesopores. Acanthopores very small,
few, practically wanting. When perfectly preserved (see plate XV, fig. 4) the cysti-
phragms are often to be seen in the mouths of the zocecia, giving them the false
appearance of being very small and situated at the bottom of a wide sloping area.

Internal structure: In the vertical sections the zoccial tubes proceed to the sur-
face in straight or curved lines, according to the form of the zoarium. They are
provided with thin walls and usually two more or less closely arranged series of
cystiphragms, one on each side of the tube, the narrow intervening space being
crossed by an approximately equal number of straight diaphragms. The variation
and relative disposition of parts is shown in fig. 6 of the plate cited. The lower half
220 THE PALEONTOLOGY OF MINNESOTA.

(Monticulipora arborea.
of the figure is taken from the lower part of the section where the transverse parti-
tions are less closely arranged than near the surface of the zoarium. The walls have
a lineo-granose structure. Tangential sections show that the zoccial tubes are
polygonal and thin-walled, the opening left by the cystiphragms ovate or sub-
ciicular and situated laterally or subcentrally. At the angles of junction the walls
are slightly thickened, and there is some evidence to show that very small acautho-
pores were developed at these points.

This fine species has an external resemblance to irregular examples of M. levis
Ulrich, from the Cincinnati group of Ohio, but the zocecia and internal structure of
M. grandis are so much larger and different that the relation between the two species
must really be quite remote. Excepting that mesopores are wanting entirely, the
interior, as brought out by thin sections, is very similar to Prasopora contiqgua Ulrich,
and I have considered the advisability of referring the species to Prasopora rather
than Monticulipora.. For the present, however, we must conclude that the absence
of mesopores and lobate-massive instead of discoid growth are features sufficient to
disbar the species from Prasopora. ,

Formation and tocality.—At the base of the Trenton shales and the top of the underiying limestone
at Minneapolis and Cannon Falls, Minnesota. Vertical range apparently very limited.

Mus. Reg. No. 5969.

MonTIcULIPORA ARBOREA, 7. Sp.

PLATE XX, FIGS. 1-9 and ly, 14.

Zoarium dendroid, rising to a hight of 4 or 5 cm.; branches subcylindrical;
dividing at intervals varing between 5 and 20 mm.; surface with low monticules, or
smooth. Zocecial apertures small, subangular, enclosed by rather thick, minutely
granulose walls, on which small acanthopores, one or two to each zocecium, are to be
distinguished from the numerous small granules, which, together with the acantho-
pores, are quickly removed when exposed to the weather. About fourteen of the
cells between those occupying the monticules or those in the clusters occur in 3 mm.
Mesopores wanting.

Internal characters: The tabulation of the zocecial tubes is compact throughout,
and very much so in the peripheral region. The tubes bend outward in a gradual
curve from the imaginary axis, and have cystiphragms from the beginning. In the
axial region these are large and about two-thirds of the tube-diameter apart, becom-
ing gradually a little nearer to each other until the fully matured condition of the
species is reached, when they recur at intervals scarcely equalling one-fourth of the
diameter of the tube. They also change their shape here, the opening which had
BRYOZOA. 221

Monticulipora (?) cannonensis.]

been lateral (see transverse section, pl. XX, fig. 3) is now narrower and produced so
that it extends nearly across the center.of the zoccial cavity. This is shown best
in tangential sections, parts of two of which are represented in figs. 4 and 6 on plate
XX. Figure 4 shows the structure immediately beneath the surface, with small
acanthopores and numerous smaller pores in the walls aud cystiphragms. In figure
6, showing the appearance at a slightly lower level, the walls are thinner and the
acanthopores apparently wanting. Figs. 13 and 14 (plate XX) represent tangential
and vertical sections of a Kentucky specimen of this species in which we note an
unusual condition, namely, in some parts of the axial region there is a total absence
of both diaphragms and cystiphragms. In other parts of the same section, however,
these structures are developed in the usual manner, so that it is allowable to assume
that their occasional absence is merely an abnormal condition. The tangential
section represents a condition very nearly intermediate between figs. 4 and 6 of the
same plate. :

In many respects this species resembles Atactoporella ramosa, occurring in the
bed of shales next beneath, but the surface of the latter is more abundantly spinulose.
Thin sections, especially tangential, are easily distinguished. The true position of
the species seems to be nearer the frondescent variety of M. mammulata d’Orbigny,
described by Nicholson from the Cincinnati rocks under the name of M. molesta.

Formation and locality.—Galena shales at several points near Cannon Falls, Minnesota, and at
Decorah, Iowa. In Kentucky the species occurs in the Trenton shales between Burgin and Danville,
and at Frankfort.

Mus, Reg. Nos. 7631, 8035. 8048, 8062.

MonTIcuLipora (?) CANNONENSIS, ”. Sp.

PLATE XX, FIGS. 10-12.

Zoarium ramose, branches subcylindrical, 6 to 9 mm. in diameter, surface even,
without monticules, but exhibiting the usual clusters of large cells. These, however,
are inconspicuous in this species. Zocecia angular, with thin walls, about twelve in
3mm. Mesopores and acanthopores apparently wanting, the occasional small cells
wedged between the ordinary zocecia being merely young or abortive.

Internal characters: All that is known of these is shown in figures 10 to 12 on
plate XX. The characteristic features are (1) the greatly crowded diaphragms and
cystiphragms, (2) the presence of the latter throughout the length of the tubes, (8)
the unusual tenuity of the walls in tangential sections, and (4) the almost total
absanoe and exceedingly small size of the acanthopores.

The generic position of this species is somewhat in doubt. The ramose habit of
growth, and all the other characters save one, are indicative of Homotrypa. This
922 THE PALEONTOLOGY OF MINNESOTA.
3 [Atactoporella.

character is the development and continuous presence of cystiphragms in the axial
region of the zoarium. In this respect the species agrees with M. arborea and M.
grandis, and differs from all species of Homotrypa in which these structures should be
developed in the peripheral region only. Even granting the importance of this
distinction it should be understood that the present arrangement of the species
is regarded as provisional.

Compared with M. arborea, the species under consideration is distinguished by
having larger zocecia and thinner walls. The internal differences will be appreci-
ated at once in comparing the various figures of the two species given on plate XX.
Homotrypa callosa, illustrated on the same plate, has thicker walls, fewer diaphragms
and no cystiphragms in the axial region.

Formation and locality.—Rare in the Galena shales, near Cannon Falls, Minnesota.

Genus ATACTOPORELLA, Ulrich.

Atactopora (part.), ULRICH, 1879. Jour. Cin. Soc. Nat. Hist., vol. ii, p. 119.

Atactoporella, ULRICH, 1883, Jour. Cin. Soc. Nat. Hist., vol. vi, p. 247; 1890, Geol. Surv. DL, vol. viii,
p. 370.

Peronopora (part.), NICHOLSON, 1881. “The Genus Monticulipora,” p. 215.

Zoarium generally forming thin crusts over foreign bodies, rarely lobate or sub-
ramose. Surface commonly with monticules. Zocecia with very thin inflected walls,
their apertures irregularly petaloid ; internally with cystiphragms. Mesopores angu-
lar, numerous, often completely isolating the zoccia; at first open and distinctly
tabulated, but, when fully matured, largely or entirely filled by a deposit of scleren-
chyma. Acanthopores very numerous, varying in size with the species, encroaching
more or less upon the zoccial cavity.

Type: Atactoporella typicalis Ulrich. ‘

The affinities of this genus are with Monticulipora on the one side and Peronopora
on the other. From the first it is distinguished by the abundant development of
mesopores and the more numerous acanthopores. These are not only usually
smaller in Monticulipora, but they also do not inflect the zoccial walls. In Peron-
opora, as restricted by me, the zoarium is bifoliate, and the mesopores are not filled
up with age in the manner characteristic of Atactoporella.

There may be in all about twelve species of this genus known to me, six of
which are described from the Cincinnati rocks in the papers cited above. The same
series of beds afford at least two new forms, and the Trenton of Kentucky and Ten-
nessee two more, while the Birdseye and Trenton of Minnesota add the following
species to the list .
BRYOZOA. 223

. Atactoporella typicalis.]

ATACTOPORELLA TYPICALIS, Var PRACIPTA, ”. var.

PLATE XV, FIGS. 16 and 17; PLATE XVIII, FIGS, 1-4.

_ This form, though much earlier, is too much like the Cincinnati A. typicalis
Ulrich (Jour. Cin. Soc. Nat. Hist., vol. vi, p. 248, 1883), to be distinguished specifically.
The resemblance is so close that the original description may, with a few trifling
alterations, be made to fit the Minnesota form. Hundreds of feet of strata, however,
intervene between the two horizons respectively held by the two varieties, in which
the species is unknown. It would seem, therefore, to be a case of reapparition, not
necessarily of the same species, but of the same type of structure, similar to the cases
of Callopora and Dekayella noticed in this work.

The characters of var precipta are as follows:

Zoarium forming small thin crusts, rarely exceeding 1 mm. in thickness, over
ramose Bryozoa and shells. Surface minutely spinulose, without monticules, except
in rare instances (see plate XVIII, fig. 4), but exhibiting at intervals of about 2.5 mm.,
measuring from center to center, clusters of cells slightly larger than the average
between which the interspaces are also a little thicker than usual. Zocecial apertures
floriform, the walls thin and at each inflection raised into a small spine, the surface
extension of an acanthopore, arranged in moderately regular, diagonally intersecting
series, averaging fourteen in 3mm. Interspaces narrowing with age, very thin, with
the zoccial walls largely in contact, the apertures direct and the mesopores small
and easily overlooked in fully matured examples; thicker, with the mesopores more
distinct and the zocecial apertures drawn out obliquely in younger stages of growth.
Acanthopores numerous, small but sharply elevated, situated in the zoccial walls,
four to seven, usually five or six, around each aperture.

Internal characters: In tangential sections the zocecial walls are very thin and
indented more or less sharply at from four to seven points in their circumference
These inflections of the wall are emphasized by the acanthopores, one of which
occurs at each point and appearing in nearly all cases to be formed on the inner
side of the wall. A few of the zocecia may be completely isolated by the interven-
tion of irregularly-shaped mesopores, but as a rule they are in contact at limited
points. The mesopores never form more than a single row, and their walls are
entirely without acanthopores. The crescentic cut edges of the cystiphragms, some-
times two or even three in each, are to be seen in each zocecium. On account of the
nearly equal thickness of these edges and of the walls of the zocecia and mesopores, it
n difficult to discriminate between the various lines shown in tangential sec-

is ofte

tions. Good vertical sections are difficult to prepare, because of the tenuity of the
224 THE PALEONTOLOGY OF MINNESOTA.

[Atactoporella insueta.

zoarium. On plate XV, fig. 16 illustrates the characters as brought out in a section
taken from a young example. The section drawn on plate XVIII; fig. 2, was pre-
pared from the thickest specimen seen. Between these two figures the student will
be able to work out the essential features without further comment. It might be
well, however, to direct attention in the last figure to the infilling and contraction
of the mesopores in the upper half. Also to the fact that some of the zoccial tubes
in vertical sections, and the same remark applies to all Bryozoa having cystiphragms,
may appear to be, in part at least, crossed by complete diaphragms. This appearance
however, is merely the result of the different directions in which the cystiphragms
cross the variotis tubes shown in the section. To obtain the characteristically curved
line of the cystiphragm it is necessary that the section pass nearly across them.
When the section passes through the tube parallel with the inner edges of the cysti-
phragms they must necessarily appear as straight or oblique lines, thus simulating
true diaphragms.

This variety differs from the typical form of the species in the following particu-
lars: The zocecia are a little larger, the mesopores less numerous and often of larger
size, the acanthopores one or two more to each zocecium, and the tabulation a little
more compact. Compared with other species, A. typicalis is readily distinguished by
the exceeding tenuity of the zocecial walls, and the greater projection inward of the
acanthopores. The latter are more numerous than in any of the other Minnesota
species known.

Formation and locality:—The types of A. typicalis are from the Utica horizon of the Cincinnati sec-
tion at Cincinnati, Ohio, and vicinity. The present variety precipta is from the middle third of the
Trenton shales at Minneapolis, St. Paul, Fountain, and other localities in Minnesota.

Mus. Reg. Nos. 5983, 5984.

ATACTOPORELLA INSUETA, 7. Sp.

PLATE XV, FIGS, 13-15; PLATE XVIII, FIGS 5-8.

Zoarium forming thin crusts over shells, crinoid columns, and ramose Bryozoa,
generally about 1 mm. in thickness. Surface with clusters of large cells at intervals
of 3.3 mm., usually little or not at all elevated, at other times rising into low and
broad monticules. Zocecial apertures in old stages subangular and with thin inter-
spaces in which the mesopores are not readily distinguishable; in younger stages more
rounded, often ovate, with the interspaces usually somewhat wider and the meso-
pores obvious ; walls thin, but little inflected. In the commonest form of the species
there are from thirteen to fifteen zoccial apertures in 3 mm., but in the variety
illustrated in figs. 7 and 8 on plate XVIII, only eleven are to be counted in the same
space, Acanthopores of medium size, two to four to each zocecium, situated in the
Atactoporella crassa.] BRYOZOA. 225

angles of junction and between the angles in the walls of both the zoccia and meso-
pores. In most cases the acanthopores are not very conspicuous at the surface.
This is in part dye-to attrition, since on protected spots they are distinct enough,
giving the surface a minutely granulose character of somewhat coarser and looser
pattern than in A. typicalis. In a variety represented by a dozen or more specimens
these structures are much more strongly developed. Indeed, these specimens
remind one very much of A. schucherti Ulrich, so far known only from the upper beds
-of the Cincinnati group in Ohio.

Internal characters: These are so well illustrated on the two plates above cited
that detailed descriptions are rendered unnecessary. It will suffice to say that the
mesopores, though usually rather large, are variable in size and distribution, that
the zocecia in the spaces between the aggregations of large cells are often in contact
with each other for more than half their circumference, that the walls are a little
thicker than in A. typicalis, the acanthopores less numerous, larger, and yet not pro-
jecting inward so much, while the tabulation of both sets of tubes is much less
compact.

As has been intimated, two varieties might be distinguised from the typical
and more common form of the species. The first differs in having larger zocecia, the
second in having much stronger acanthopores, these being larger and prominent
enough at the surface to obscure the view of the zocecial apertures. The latter may
be compared with A. crassa, the following species, but they are too distinct in verti-
cal sections to be confused.

~

Formation and locality—Middle third of the Trenton shales at Minneapolis, St. Paul, Fountain, and
other localities in Minnesota where that horizon is exposed.

Mus. Reg. No. 5985.

ATACTOPORELLA CRASSA, 7. sp. |

PLATE XV, FIGS. 18-21.

Zoarium a small, irregularly hemispheric mass, growing upon some foreign object,
9 or 3 cm. in diameter and 5 to 10 mm. in hight. Surface without monticules, nor
have distinguishable clusters of either large or small cells been detected. Zocecial
apertures subangular, rounded or irregularly outlined, inclosed by thick walls, prom-
inently elevated at most of the angles of junction into strong acanthopore spines ;
about fourteen apertures in 3mm. Mesopores less numerous than usual, small and
difficult to detect at the surface. ;

Internal characters: Considerable variety of structure, depending upon age, is
exhibited in different tangential sections or in parts of the same section. These, as

—15
226 THE PALEONTOLOGY OF MINNESOTA.

[Atactoporella ramosa.

is shown in figures 18 to 20 (pl. XV), consist of a gradual thickening of the zocecial
walls, and strengthening of the acanthopores, causing the mesopores, which in the
thin-walled regions are large and distinct enough, though never. as,numerous as in
most other species of the genus, to be more or less completely obliterated. Cysti-
phragms occur in every zocecial tube. The opening in them varies from subcircular to
semiovate, according as they are situated subcentrally or at one side of the zocecium.
Vertical sections (pl. XV, fig. 21) show that the cystiphragms and diaphragms in both
sets of tubes are equally crowded. It is, therefore, difficult to distinguish the meso-
pores from those zocecial tubes in which the curved section of the cystiphragms is
not shown.

This is a well marked species and readily separated from A. schucherti Ulrich,
and certain varieties of A. insueta, which it resembles chiefly in the large size of the
acanthopores, by the much greater abundance of transverse partitions in the tubes.
The zoarium is also heavier, and the zoccial walls thicker. A nearer relative
apparently than either of the species compared is found in an undescribed species
occurring near the tops of the hills at Cincinnati, Ohio.

Among associated species that might be confounded there are two of Leptotrypa,
one, a parasitic undescribed form, the other, subglobular, described in this volume
as L. acervulosa. Both are distinguished externally by having much thinner walls
and inconspicuous acanthopores. When sectioned the Leptotrypas will of course be
separated at once by the total absence of cystiphragms.

Formation and locality Galena shales, St. Paul and near Cannon Falls, Minnesota. ©

<

ATACTOPORELLA RAMOSA, 1. SD.

PLATE XX, FIGS. 22-27.

Zoarium erect, subramose, branches compressed, dividing once or twice, 3 to 6
mm. thick, 5 to 10 mm. wide. Surface minutely spinulose, and elevated at intervals
of about 2 mm. into small monticules, varying in different examples from low and
rounded to prominently conical in shape. Slopes of monticules occupied by cells of
slightly larger size than the average; their summits, however, often appear solid,
these being, in most cases, formed by small aggregations of closed | mesopores.
Zocecial apertures small, floriform, about sixteen in 8 mm., separated by interspaces,
in which but few mesopores can be detected, of less width than their diameter;
each surrounded by from five to seven small acanthopores, projecting well into the
zocecial cavity. This describes the fully matured and ordinary appearance of well
preserved specimens. Young stages are quite different, the zocecial apertures being
Atactoporella ramosa.] BRYOZOA. : 227
a little larger, angular, with very thin walls, and while the mesopores are readily
distinguishable and one or two to each zocecium, the acanthopores are so small as
to be practically wanting.

Internal characters: To obtain the fully matured characters of this species it
is necessary to make the tangential section as nearly superficial as possible. In
this outermost region the zocecial wells are of moderate thickness and inflected more
or less strongly at the points occupied by the acanthopores. The mesopores here
appear as mere irregular interstices between the rounded walls of the zocecia. At
deeper levels in the section the acanthopores become smaller and at last indetermin-
able, the zocecia prismatic and their walls thin, and the mesopores more distinct.
The appearances now are just as in transverse sections of the axial region. Vertical
sections show that cystiphragms and diaphragms are developed throughout the
tubes from their origin in the axial region to their superficial orifices. These struc-
tures are, however, a little more closely arranged near the surface of the zoarium
than in the axial region. Mesopores are likewise present in both regions, but these
seem gradually to expand as they bend out of the axial region and to assume the
characters of true zocecia. At the same time new mesopores are interpolated, but
these do not develop into zoccia. On the contrary the tendency is to close them up
by deposit on the zocecial walls.

This is the second species of the genus in which the zoarium rises into the
ramose form. The first is the A. newportensis Ulrich, from the lower beds of the
Cincinnati group at Newport, Ky. The latter has larger monticules, more numerous
mesopores, less abudant acanthopores, and thinner zocecial walls. The ramose habit
of growth will distinguish it from the other species of the genus. Several species
externally similar, but internally widely different, occur in the same beds with
A, ramosa. One of these is the Callopora pulchella, var. persimilis, another is the
Homotrypa tuberculata of the present work, while a third is the Batostoma montuosum.
With a little practice these will be distinguished readily enough, even without the
aid of thin sections. When the surface is a little worn the student may find it diffi-
cult to separate the species from montiferous examples of Monticulipora arborea, a
species found chiefly in the overlying Galena shales. When both are in a good
state of preservation he will find that the walls of the Monticulipora are somewhat
thicker and much more minutely granulose, and that true mesopores are wanting.

Formation and locality.—Upper third of the Trenton shales, near Cannon Falls, Minnesota, where it
is associated with an abundance of Prasopora conoidea and Phylloporina corticosa.
228 : THE PALEONTOLOGY OF MINNESOTA.
|Homotrypella.

Genus HOMOTRYPELLA, Ulrich.

Homotrypella, ULRicH, 1886. Fourteenth Ann. Rep. Geol. and Nat. Hist. Surv. Minn., p. 83.

Zoarium somewhat irregularly ramose, occasionally palmate or frondescent ;
monticules wanting, but small macule, consisting of clusters of mesopores, often
present. Zocecia with rounded apertures, the latter sometimes inflected by the acan-
thopores. Mesopores small, abundant, in some cases completely isolating the zocecia.
Acanthopores abundant, of medium size, generally imparting to the surface a min-
utely granulose character. Cystiphragms developed chiefly in the median region
of the zocecial tubes, being absent usually just beneath the surface and never present
in the axial region.

Type: HH. instabilis Ulrich.

This genus was established for the reception of a small but eminently natural
group of Lower Silurian species that could not be included in any of the other
genera of the family. Since then other forms have been discovered, and the classi-
fication of several others changed, so that now no less than eleven, perhaps twelve,
species of the genus are known to me. These range from the Birdseye to the top of
the Lower Silurian, each of the more important subdivisions containing one or more
species.

In the ramose habit of growth the genus resembles Homotrypa Ulrich, but the
abundant mesopores are a distinguishing mark of some importance. A comparison
with Peronopora Nicholson, and Atactoporella Ulrich, shows the following differences :
In the first the zoaria are bifoliate, in the second usually parasitic, and in both the
cystiphragms are developed in an almost uninturrupted series throughout the length
of the zocecial tubes.

Fuller investigations into the affinities of these fossils have shown good grounds
for redistributing the species heretofore referred to Batostomella. That genus must,
therefore, be restricted to the Devonian and Carboniferous species originally
intended as types.* This leaves the Lower Silurian species unplaced generically.
Since large specimens of B. gracilis Nicholson, and many of the ordinary forms of
B. meeki James, sp., from the Cincinnati group of Ohio, often have a few cystiphragms
developed in the curve of the tubes, and as their other characters are in no wise
strongly opposed to a union with Homotrypella, it seems best, at any rate provision-
ally, to place them here. However, the B. simulatriz Ulrich, group of species cannot
be admitted, and to accommodate them a new generic name will have to be proposed.

 

 

*Trematella, Hall, 1887, Pal. N. Y., vol. vi, p. 14, is evidently a synonym of Batostomella, Ulrich, 1882, Jour. Cin. Soc. Nat
Hist., vol. v, p. 154. * '
BRYOZOA. 229

Homotrypella nstabilis.]

The latter continue into the Lower Helderberg and may really be the stock that
| eventually produced Batostomella annulata (Trematella annulata Hall) and B. perspin-
wlata Hall, sp., of the Devonian, and B. spinulosa Ulrich, the Chester type of the
genus. But I am satisfied that the gracilis group, indeed the whole genus Homotry-
pella, did not survive into the Niagara.

Homotryretua instapitis Ulrich.
PLATE XVIII, FIGS. 9-20.

Homotrypella instabilis ULRICH, 1886. Fourteenth Ann. Rep. Geol. and Nat. Hist. Surv. Minn., p. 83.

Zoarium ramose, growth rather irregular; branches rounded, sometimes nodular
or lobate, and varying in diameter from 3 to 8 mm.; surface generally without mon-
ticules, and when these are present they are low and broad ; small macule or clusters
of mesopores are not infrequently present. Superficial characters of zocecia and
mesopores variable. In some, and these are in most cases well-preserved examples,
the zocecial apertures are irregular both in form and arrangement, with thin walls,
partly separated by mesopores numbering one or two to each zocecium, In these
specimens the acanthopores are small yet prominent and sharp, and number from
one to three to each zocecium. ‘The mesopores are always smaller than the zocecia,
but vary occasionally in shape, size and arrangement. In many other examples
both the zocecia and mesopores are smaller and their walls correspondingly thick,
while the acanthopores are blunt and thicker. In most cases a little wearing suffices
to obscure the mouths of the mesopores, ¢o that they are readily overlooked. Twelve
or thirteen of the zocecia occur in 3 mm.

Internal characters: As may be seen by comparing figures 13 and 14 with 18 and
20 (plate XVIII) tangential sections of this species present an unusual variety of
' appearances. In the majority of sections, providing they are not too deep, the walls
of the cells are very thick, with not a sign of cystiphragms in the zocecial cavities.
When a second or peripheral series of cystiphragms has been developed (see figs.
17-20) a very different appearance is obtained. Now the walls are thinner, and a
cystiphragm, leaving from one-third to one-half of the zocecial cavity open, is to be
seen in each of the zocecia. In all cases the polygonal lines of contact between the
two sets of cells is sharply defined, and the walls of both approximately of equal thick-
ness. The acanthopores are conspicuous features of these sections, but their rela-
tive abundance varies somewhat in different examples. In the axial region of verti-
cal sections the walls of the tubes are very thin and finely wavy, and the diaphragms
ght and remote, or wanting entirely. As the tubes enter the peripheral region

stral
the number of diaphragms is greatly increased, the walls thickened, and cystiphragms,
230 THE PALEONTOLOGY OF MINNESOTA.

[Homotrypella multiporata.

mesopores and acanthopores developed. The mesopores are distinguished from the
zocecia by their shortness and in having no cystiphragms. The latter structures
number from three or four to fifteen in a direct series in each zocecial tube. In
most cases they occur only in the region intervening between the fully matured
peripheral and the immature axial region. Beyond them the diaphragms are crowded
and essentially horizontal. In the mesopores the diaphragms are often thick and
situated about the same distances apart as in the zoccial tubes, with from fourteen
to seventeen in 1 mm. In the axial region of transverse sections the zocecial tubes
are of unequal sizes and of peculiarly irregular shapes.

Formation and locality.—Rather abudant in the middle third of the Trenton shales, at St. Paul.
Minneapolis, Cannon Falls, near Fountain, and other localities in Minnesota.

Mus. Reg. Nos. 5025, 5981, 5982.

HomMoTRYPELLA MULTIPORATA, %. Sp.

PLATE XVIII, FIGS, 21, 22.

Zoarium ramose, branches cylindrical, 8 or more mm. in diameter. Zocecia
small, about twelve in 3 mm., with thin walls, rounded or petaloid apertures, their
margins raised slightly and separated by a conplete ring of small mesopores. Acan-
thopores small, numerous. Cystiphragms seen only in the turn of the zocecial tubes,
as far as observed, varying between two and six in each tube. Diaphragms in zocecial
tubes exceedingly delicate, five or six in 1 mm.; a little stronger in the mesopores,
and here numbering about nine in each tube ; apparently wanting in the axial region,
where the tube walls are minutely crenulate and thin. In the axial region of trans-
verse sections the tubes are very unequal.

This species, so far as observed, forms thicker branches, has much more numer-
ous mesopores, and smallér and thinner-walled zocecia than its associate H. instabilis.
Internally the diaphragms are wider apart in both sets of tubes and more delicate.
‘They differ again in being twice as numerous in the mesopores as in the zocecial
tubes. None of the other species are sufficiently related to require comparisons.

Formation and locality.—Rare in the middle third of the Trenton shales, at St. Paul and Minne-
apolis, Minnesota. .
HomorrPELLA (?) SUBGRACILIS, n. sp.
PLATE XXVI, FIGS. 10-16.
Zoarium small, ramose, dividing irregularly; branches subcylindrical, 2 to 4.5
mm, in diameter ; surface without monticules and macula. Zoccia rather irregular

in size, shape and arrangement, varying also in the thickness of their walls, these
being often stronger than shown in figs. 15 and 16, plate XXVI; twelve or thirteen
BRYOZOA. 231
Homotrypella (?) ovata.]

in 3 mm. Apertures oblique in some of the young examples, nearly or quite direct
in the others; in the latter the numerous small acanthopores cause more or less
irregularity in the outline of the apertures. Mesopores of unequal sizes, irregular in
arrangement, scarcely more numerous than the zocecia, from which it is sometimes
difficult to distinguish some of the larger ones.

Internal characters: These are but illy preserved in the two sets of sections
prepared, and all the characters shown in them are brought out in figs. 10, 11 and
12, on plate XXVI. Four vertical sections fail to exhibit any positive evidence of
either diaphragms or cystiphragms, the tubes appearing as open throughout. This
condition, however, seems unnatural and probably due to imperfect preservation.
There should be some transverse partitions in the tubes, though these, especially
the cystiphragms, must have been comparatively few in this species. A similar
absence of diaphragms, in this case obviously due to imperfection, is sometimes met
with in sections of H. gracilis (Chetetes gracilis Nicholson), of the Hudson River rocks,
which the present species is believed to resemble more than any other. And yet I
am satisfied that, when sufficiently good material can be studied, the internal char-
acters will prove equally as near to those of the associated H. instabilis, with which I
had at first confounded it.

Formation and locality.—Rather rare in the middle third of the Trenton shales, at Minneapolis and
St. Paul, Minnesota.

HomoTRYPELUA (?) OVATA, ”. sp.

PLATE XVIII, FIGS. 23-30.

Zoarium small, ramose, branches generally compressed, sometimes subcylin-
drical, varying between 2 and 5 mm. in diameter or width, dividing at unequal inter-
vals. Surface without. monticules, but exhibiting at intervals of 2 or 3 mm. clusters
of cells of larger size and more widely separated than the average. Zocecial apertures
rounded, commonly a little oblique, oval and enclosed by a thin but slightly elevated
peristome on which a single small acanthopore is in most cases to be detected,
though generally with some difficulty. Interspaces depressed, with the mouths of
the rather large mesopores occupying*them, closed or open, probably according
to the state of preservation. The zocecial rims are nearly always in contact with
each other at limited points, yet many individual zocecia, especially of those in the
clusters mentioned, may be completely separated from their neighbors by mesopores.
In some specimens, preserved unusually well, the interspaces are granulose, the
granules seeming to form rows on the walls separating the mesopores. Long diam-
eter of average zocecium 0.17 mm.; some of the largest in the clusters 0.25 to 0.30

mm.; ten to twelve in 38 mm.

}
232 THE PALEONTOLOGY OF MINNESOTA.

[Homotrypella mundula.

Internal characters: Vertical sections show that the peripheral region is narrow,
that here, and in the turn of the zocecial tubes, the diaphragms are closely arranged,
with from six to eight in0.6mm. Justin the turn of the tubes, along the upper wall,
oue, two or three cystiphragms were developed. The mesopores begin at the same
point, and in these the diaphragms are more crowded and thicker. In the central
part of the axial region the tubes are larger than farther out, and intersected by
diaphragms at intervals of about 0.5 mm. In nearing the surface the tubes become
narrower and the diaphragms closer. Tangential sections are distinctive in showing
the wide interpaces, large and sharply-defined mesopores, and the ring-like defi-
nition of the zocecial walls. In most cases the zocecia are completely separated or
rarely touch each other without sacrificing any of their roundness of outline.

Compared with other species, the, Homotrypa ? intercalaris of this work seems
to be the nearest and distinguished chiefly in vertical sections, diaphragms being
absent in the axial region of that species and cystiphragms more numerous in the
peripheral. For further remarks on this relationship, see p. 216. For comparisons
with H. mundula, see under that description.

Formation and locality.—Galena shales, near Cannon Falls, Minnesota. Two fragments from the
middle Trenton shales at Minneapolis seem to be identical in nearly every respect, but so far the species
has not been found in the upper third of the shales intervening between these two horizons.

Mus. Reg. No. 8124.

HomotTRYPELLA MUNDULA, 2”. sp.

 

Fig. 12. Homotrypella mundula Ulrich, Galena shales, Decorah, Iowa.

a, tangential section; b and c, opposite sides of a vertical section, showing differences in the number
of cystiphragms; all x 18.

Zoarium dendroid, branches subcylindrical, small, 2.5 to 5.0 mm. in diameter,
dividing, generally dichotomously, at irregular intervals. Monticules wanting, but
in most cases clusters of zocecia, slightly larger and more widely separated than the
average, are to be distinguished. Zocecial apertures somewhat irregularly distributed,
BRYOZOA. 233

Homotrypella mundula.]

ten to twelve in 3mm., slightly oblique in young stages, ovate or irregular in shape,
in the best preserved examples more or less obscured by the rather large and abund-
ant projections of the acanthopores. Interspaces varying, even in small spaces, from
contact between the zocecial walls to a width fully equalling the diameter of a zocec-
ium. Where widest they are depressed, and in a few instances show the mouths of
mesopores, but as a rule these appear as closed solidly.

Internal characters: In the axial region of vertical sections the tubes sometimes
appear to have grown irregularly, and where this is the case they are intersected by a
few remote diaphragms. However, in the normally developed straight tubes, these
structures are wanting in the axial region except in zones, 2 or 8 mm. apart, extend-
ing through the branches. In these each tube has a few. Such a zone is shown in
the upper part of figs.b and c. As the tubes turn to enter the peripheral region, dia-
phragms become numerous, and in their midst a series of cystiphragms is developed in
most of the tubes. The development of the cystiphragms is not uniform, being, as
shown at 7. c., fig. 6, often isolated, while in other cases they may form continuous
series of as high as ten or twelve. Such extremes may be noted in a single section,
and it seems evident that in the development toward H. gracilis Nicholson, sp., they
had by this time lost some of their importance and.were gradually being dropped.
The mesopores are inconspicuous features in vertical sections, being filled almost
solidly with sclerenchyma in which their diaphragms are but illy distinguishable.

In tangential sections the zocecia commonly present a dark ring-like investment,
in which the sharply defined acanthopores are mostly situated. The interspaces are
of a lighter color, and but rarely exhibit any positively defined mesopores. Cysti-
phragms, so far as observed, may be detected in perhaps half of the zocecia.

A closely related but smaller species than H. granulifera (Chetetes granuliferus
Ulrich) from the Trenton of Kentucky. In its general aspect it is exceedingly like
H. gracilis Nicholson, sp., of the Hudson River rocks, and it is almost certain that
the two represent stages in one line of development. However, comparative abund-
ance of cystiphragms in the present species will distinguish them at once, these

structures being of very rare occurrence in H. gracilis. In the latter the acantho-
pores also are smaller, so that the surface granulation is less coarse.

Formation and locality —Galena shales. Common at Decorah, Iowa; rare in the vicinity of Cannon
Falls, Minnesota.

Mus. Reg. No. 8080,
234 THE PALEONTOLOGY OF MINNESOTA.

(Homotrypella rustica

HomotTryPELLA RUSTICA, 1. sp.

PLATE XVIII, FIGS. 31-33.

Zoarium irregularly ramose, branches 5 to 10 mm. in diameter. Low swellings
of the surface, scarcely to be called monticules, occasionally present. Surface very
rough under a hand lens, the acanthopores being strong and numerous, though not
materially inflecting the zocecial walls. Zocecial apertures rounded, about eleven in
3mm. Mesopores abundant, though but rarely separating the zocecia completely,
of unequal sizes, rounded at the surface. i

Internal characters: In tangential sections, showing the characters immediately
beneath the surface, (upper part fig. 32) the zocecia are rounded, with only moder-
ately thick walls, the mesopores sharply defined, subangular, of unequal sizes, and
averaging three or four to each zocecium, the acanthopores strong, perhaps two to
each zocecium, and situated chieflly in the zocecial walls, which they occasionally
only cause to bend inwardly. At a deeper level (lower part fig. 32) the walls are
thinner, the acanthopores smaller, and the mesopores larger. At both levels the
zocecia almost uniformly exhibit the cut edges of cystiphragms. In vertical sections
the most striking feature of the species is the abundant tabulation of all the tubes.
Diaphragms occur all through the axial region, and both the mesopores and acantho-
pores began earlier than usual. The outward curving of the tubes also is unusually
gradual. The diaphragms in the two sets of tubes are subequally distributed, and
it is often difficult to discriminate between them when the curved edges of the
cystiphragms are not shown. At about the middle of the curve nine or ten dia-
phragms occur in 1 mm.; nearer the surface they are a little closer, while more toward
the center of the branch they are further apart. The cystiphragms are unusually
superficial in this species, forming crowded series almost to the mouths of the
zocecia.

This species is distinguished from H. granulifera and H. mundula by the greater
number and open character of the mesopores; from H. multiporata by its larger
zocecia, fewer and more unequal mesopores, and more crowded as well as different
tabulation of the tubes. H. instabilis has thicker walls, and is quite different in other
respects.

Formation and locality.—The sections illustrated were prepared from a single example collected by
the author in the upper beds of the Hudson River group, at Spring Valley, Minnesota. This specimen

seems identical with a common species occurring at an equivalent horizon in Indiana and Ohio, to which
I had applied the name rustica in my MS. notes.

Mus, Reg. No. 8125..
Howotrypa.] BRYOZOA. 935

Genus HOMOTRYPA, Ulrich.

Homotrypa, ULRIGH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 240; 1890, Geol. Surv. IIl., vol. viii,
pp. 370 and 409; 1883, Foorp, Contri. Micro-Pal, Can., pt. I, p. 9.

Zoaria erect, generally ramose, at other times frondescent, with or without mon-
ticules. Zocecial tubes with very thin and finely crenulated walls and remote dia-
_ phragms in the axial region. Cystiphragms, isolated or in series, developed in the
peripheral region only. Apertures polygonal or subcircular, the shape depending
upon the thickness of the walls and the character of the interspaces. Mesopores
occasionally wanting, typically few and gathered into clusters ; in several aberrant
cases (e. g. H. separata), comparatively numerous and causing a greater or less separa-
tion of the zocecial walls. Acanthopores usually present, of varying sizes. What

appear to be large communication pores have been detected under favorable circum-
stances in several species. :

Type: H. curvata Ulrich, Hudson River group.

This is the largest and one of the best characterized genera of the T'repostomata.
Adding the new forms here proposed we have a total of seventeen described species.
There are at least six more to be published from the Hudson River Rocks of Ohio
and Indiana alone, while as many more are known to me from various Lower Silu-
rian horizons in Tennessee, Illinois, Wisconsin and Minnesota. :

The affinities of the genus, as indicated by species like H. intercalaris, are with

Homotrypella; others resemble Eridotrypa, while some again are not easily distin-

“guised from erect forms of Monticulipora like M. arborea and M. molesta Nicholson.
In this connection it would be well to read the remarks on pp. 215 and 216.

Homotrypa MINNESOTENSIS Ulrich.
PLATE XIX, FIGS. 1-9.

Homotrypa minnesotensis ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p.79.

Zoarium ramose, branches subcylindrical, from 5 to 15 mm. jn diameter, gener-
ally dividing dichotomously at long intervals, rarely inosculating. In the typical
form monticules are not developed, but the clusters of large cells are conspicuous.
In a later variety, commonly also of larger size than the typical form, these clusters
are often raised into prominent monticules, about 2.5 mm. from center to center.
Central part of these groups often appearing subsolid or with shallow mesopore-like
depressions in the interspaces. True mesopores wanting. Acanthopores exceedingly
small and few, observed only in thin sections. Ordinary zoccia angular, with thin
236 THE PALEONTOLOGY OF MINNESOTA.

(Homotrypa exilis.

walls and more or less oblique apertures. In young examples the obliquity is very
great, while it is only in the largest that the apertures can be said to be direct. About
twelve of the average zocecia in3mm. In the large monticulose variety, already men-
tioned, and which may be designated as var. montifera, there are thirteen apertures
in the same space.

Internal characters: In vertical sections the peripheral or “ mature” region is
very narrow, and the axial region, in which the tubes are long and nearly vertical,
correspondingly large. Inthe latter diaphragms are wanting, and the walls extremely
thin and wavy. Near the surface the walls are appreciably thickened, but never
enough to be described as otherwise than thin. The curve of the tubes throughout
is unusually gentle. Diaphragms and cystiphragms set in abruptly and their arrange-
ment in the tubes is shown better in figs. 1, 5 and 6 than it can be described.

Owing to the obliquity of the zocecial apertures it is difficult to prepare satis-
factory tangential sections of any except large and old examples. The successful
ones show that the zocecial walls are comparatively thin, that a few mesopore-like
cells are sometimes interpolated between the zocecia, and that the acanthopores are
so small and few that they are readily overlooked. Nor are the cystiphragms con-
spicuous in these sections.

Transverse sections are interesting chiefly because they show the unusual nar-
rowness of the peripheral region, and the decrease in size and flattening of the tubes
as they enter this part of the zoarium. ,

This species is distinguished from all the others of the genus known from the
Trenton by its oblique zocecial apertures.

@

Formation and locality —Common in the lower third of the Trenton shales, at Minneapolis, St.
Paul, Cannon Falls, Preston, Fountain and other localities in the state. It has not been certainly identi-
fied in the middle third of the shales, but in the upper third, at St. Paul, a large form of this species occurs
associated with the var. montifera in considerable abundance. The species is also known from Decorah
and other localities in Iowa.

Mus. Reg. Nos. 5970, 5975, 7600.

Homotrypa exiLis Ulrich.
PLATE XIX, FIGS. 10-16.

Homotrypa exilis ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 80.

_Zoarium ramose, branches slender, without monticules,, cylindrical, 3 to 5 mm.
in diameter (generally 4 mm.), dividing at long intervals. Entire hight of zoarium
less than 75 mm. Zocecia with rounded, direct apertures and moderately thick
walls, about twelve in 3mm. Clusters of cells larger than the average occur, but
do not constitute a conspicuous feature. Mesopores comparatively numerous,
BRYOZOA. 937

Homotrypa separata.] +

especially in the clusters just mentioned. Diaphragms wanting in the axial region,
but present in the short and rather abruptly bent peripheral region, in which the
walls are also thickened and a series of cystiphragms developed.

This clearly is not the young of H. minnesotensis. The specimens viewed under
a hand lens show more direct and rounder zoccial apertures, with the mesopores
also more abundant, and on the whole have a more matured appearance than many
much larger specimens of that species. Furthermore, the zocecial walls in the larger
species never get to be as thick as has been observed in sections of fH. exilis.

Formation and locality.—Not uncommon in the lower third of the Trenton shales at Minneapolis,
Minnesota.

Mus. Reg. Nos. 5976, 7655.

HomotrypPa SEPARATA, 7. Sp.

PLATE XIX, FIGS. 17-20,

In its growth and, with the exception of one feature, also in its internal charac-
ters, this species is very similar to H. minnesotensis. As it also occurs in the same
beds with that species, a detailed description is unnecessary. A comparison of the
two forms brings out that H. separata has an abundance of mesopore-like depressions
at the angles of junction between the zocecia, with aggregations of such depressions
in the maculz (see fig. 19), causing the zocecial apertures to be rounded—commonly
subcircular instead of angular. Internally these interspaces give, to tangential sec-
tions especially, a very different appearance from those of H. minnesotensis (compare
figs. 3 and 4 with 17 and 18, plate XIX), Vertical sections of the two species are
more alike, the only difference worthy of notice being the numerous presence
of mesopores in the one and almost total absence in the other. Despite the obvious-
ness and, in most other cases, the importance of a difference like that existing
between these two forms, I cannot doubt that they are in reality closely related.

Formation and locality.—Lower third of the Trenton shales at Minneapolis, Chatfield, and near
Preston, Minnesota.

Mus. Reg. Nos. 7667, 8122.
238 THE PALEONTOLOGY OF MINNESOTA.

{Homotrypa (?) intercalaris.

“Homotrypa (?) INTERCALARIS, 7. Sp.

 

Fia. 13. Homotrypa (?) intercalaris, n. sp., middle Trenton shales, Minneapolis, Minnesota. Collec-
tion of E. O. Ulrich. a and 6, a specimen of the natural size, and small portion of its surface x18, showing
unusually oblique zocecial apertures; c and d, similar views of a fragment of a form doubtfully referred to
this species, having somewhat smaller zocecia and mural papille; e and f, similar views of a typical
example; g, more slender fragment, natural size; h, tangential section, x18, showing structure immediately
beneath surface of fully matured example; 7, another portion of same section, showing structure at a deeper
level; j, vertical section, x18, showing the peripheral region with the mesopores and cystiphragms, and a
smal} part of the untabulated axial region. ;

Zoarium small, ramose, branches subcylindrical, generally 2.5 to 3.5 mm. in
diameter. Surface without monticules but exhibiting distinct clusters of large cells
in the centers of which there is often a small aggregation of mesopores. Zoccial
apertures rounded or subangular, commonly direct to the surface, at other times
more or less oblique, occasionally so much so (see fig. 13 5) that they recall those of
Ceramoporella. The last condition probably occurred only when a new layer of zocecial
tubes was developed in which the individual cells failed to correspond exactly with
those of preceding layers. Typical form with about thirteen zocecia in 3 mm.; the
variety, also figured above, has fifteen in the same distance. Walls or interspaces
of moderate thickness, commonly with very few and inconspicuous acanthopores.
But in the variety a row of minute papilla has been observed along the center of
the wall. Mesopores rather abundant, occurring at most of the angles of junction
between the zoccia.

The internal structure is brought out sufficiently in the accompanying cut.
Figures h and 7 show how very similar tangential sections may be to those of the
BRYOZOA. 939

Homotrypa subramosa.]

later Homotrypella (?) ovata, illustrated on plate XVIII. The mesopores are on the
whole smaller and do not separate the zocecia so completely, and sometimes the dif-
ference in these respects is greater than is shown in the illustrations. The difference
between vertical sections of the two forms is better marked, the cystiphragms being
more numerous and diaphragms wanting in the axial region in the present species.
Homotrypa exilis is another closely allied form, but differs in the opposite manner,
the: mesopores being fewer (see plate XIX).
This is an important stage in the line of development discussed on page 216.

Formation and locality.—Middle third of the Trenton shales at St. Paul and Minneapolis, Minnesota.

Homotrypa susramosa Ulrich.
PLATE XIX, FIGS. 21-28,

Homotrypa subramosa ULRICH, 1886. Fourteenth Rep. Geol: Nat. Hist. Sur. Minn., p. 81.
Homotrypa insignis ULRICH, 1886. Fourteenth Rep. Geol. Nat. Hist. Sur. Minn., p. 82.

Zoarium subramose, frequently though irregularly divided ; branches compressed
or subcylindrical, their extremities often bulbous. Size of branches varying greatly,
the smallest 4 or 5 mm. in diameter, the largest 6 to 9 mm. thick, and as much as
25 mm.wide. Average specimens are about 6 mm. thick and between 8 and 12 mm.
wide, with the total hight of zoarium rarely exceeding 60 mm. Surface without
monticules, nor are the clusters of large cells very conspicuous. Zocecia with rather
thin walls and polygonal, direct apertures ; twelve to fourteen in 3mm. Zocecial
apertures shallow, exposing the cystiphragms when in a good state of preservation.
These structures leave but a small opening, and when the fossil has suffered a little
from attrition (a frequent occurrence in the beds holding the species most abun-
- dantly) in which case the true walls are obscured or cut away, the appearance is very
deceptive, the apertures seeming to be very small and oblique, and much the greater
part of the surface occupied by wall-substance. Acanthopores varying in number
and size, sometimes as numerous as two to each zocecium. More commonly the
number is little more than half that extreme. In many cases they are large enough
to constitute a marked external feature. In others, however, apparently in an
equally good state of preservation, they are so small that it is difficult to detect
them even with the aid of a good lens.

Internal characters: Vertical sections show that the tubes proceed in a gradually
increasing curve from the axial region outward to the peripheral region, in which
they are approximately at right angles to the surface; that in the axial region the
tubes are rather large, with wavy walls, and crossed by straight or oblique dia-
phragms, either in zones or occurring at intervals varying from one to three times
240 THE PALEONTOLOGY OF MINNESOTA.

“4

[Homotrypa tuberculata.

their diameter ; that in the peripheral region the walls are moderately thickened,
and the tubes occupied by a gradually crowding series of cystiphragms. The varying
appearances of tangential sections are sufficiently exhibited in figs. 22 to 25. The
differences so far observed in these sections consist almost entirely of variations in
the number and size of the acanthopores.

CGireatly increased collections, and the study of numerous sets of thin sections,
have convinced me of the specific identity of H. subramosa and H. insignis. The
latter name might be retained in a subordinate sense for the Galena shales variety,
in which the clusters of large cells are more conspicuous, the average size of
the zoarium smaller, the zocecial walls thinner, and the acanthopores permanently
less numerous and-smaller than in the typical middle and upper Trenton shales
form of the species. _.

The tabulated axial region, more numerous and larger cystiphragms, the
presence of acanthpores, and the irregular and more compact growth, will distin-
guish the species from preceding forms of Homotrypa. Thin sections will of course
separate it at once from outwardly more similar species, belonging to other genera,
that are associated in the same beds.

Formation and locality.—H. subramosa is rare in the middle third of the Trenton shales at several
localities in St. Paul and Minneapolis, but is much more abundant in the upper third of the shales at St.
Paul and localities in Goodhue county, Minnesota. The restricted var. insignis is comparatively rare in
the Galena shales at localities in Goodhue and Fillmore counties; also in the same beds at St. Paul, and
at Decorah, Iowa.

Mus. Reg, Nos. 5977 to 5980, 8030, 8061.

HomotTrypa TUBERCULATA, %. Sp.°

 

Fia. 14 Homotrypa tuberculata, n. sp., upper third Trenton shales, near Cannon Falls, Minnesota.
Collection of E. O. Ulrich. a, fragment of the natural size; b, small portion of a vertical section, x 18,
showing two mesopores, the cystiphragms and diaphragms of the peripheral region, all of which are want-
ng in the axial region; ¢ and d, two portions of a tangential section of a fully matured example, x 18, the
former showing appearance immediately beneath the surface, the latter at a slightly deeper level.
BRYOZOA. 94]

Homotrypa tuberculata.]

Zoarium small, ramose, branches rounded or flattened, dividing rather fre-
quently, 2.0 to 3.5 mm. thick, and 2.5 to 7.0 mm. wide. Surface more or less
strongly tuberculated, the monticules 2 to 2.5 mm. apart, conical, often very prom-
inent. Zocecial apertures nearly fourteen in 3 mm., angular or rounded, more or
less oblique except in the oldest examples, in most specimens exposing the cysti-
phragms. Walls thin, often separating so as to form considerable interspaces in
which a greater or less number of closed mesopores is contained. The extent of
these interspaces varies greatly, being sufficient in some instances to cause the
zocecial apertures to be of wounded or ovate form, while in other specimens they are
scarcely appreciable. Acanthopores small, about one to each zocecium.

Internal characters: In vertical sections the tubes are large and without dia-
phragms in the axial region, the latter, together with short and rather irregular
series of cystiphragms, being developed in the narrow peripheral region only.
The mesopores appear as shown in the figure. Of tangential sections it would be pos-
sible to select small portions differing so much from each other in the number of
mesopores that they would scarcely be suspected of belonging to one species. Still,
if the sections are large enough each will contain some parts that may be said to be
practically the same as those represented in figs. c andd. The acanthopores, though
small and few, are quite distinct in these sections.

This is another of those aberrant forms of the genus like H. imtercalaris. While
its relations seem often to be decidedly suggestive of Homotrypella (?) ovata, I do not
believe that its development resulted in that form. It seems to be an offshoot, per-
haps from that line, which latter produced the H. obliqua Ulrich, of the Oincinnati

group.
The strong monticules distinguish the species from the Trenton forms of the
genus. Associated with it there are two really very distinct though dangerously
similar species. The first of these is the Ataa@oporella ramosa with its numerous
acanthopores and inflected zoccial apertures, and totally different internal struc-
ture. The second, Callopora persimilis, differs so widely in its internal structure
that it will be sufficient to refer the student to the figures on plate XXII. Other
species presenting more or less superficial resemblance might be mentioned, but I
cannot regard it as necessary, since with the aid of thin sections the student will

have no trouble in distinguishing them.

Formation and locality. —Upper third of the Trenton shales, near Cannon Falls, Minnesota. The
‘species probably occurs in the same beds at St. Paul.

Mus. Reg. No. 8123.

—16
242 THE PALEONTOLOGY OF MINNESOTA.

[Homotrya similis.

Homorrypa simitis Foord.
PLATE XX, FIGS. 28-33.

Homotrypa similis Foorp, 1883. Contri. Micro-Pal. Cambro-Sil. Rocks, Canada, p. 10.

Zoarium of medium size, ramose, the branches subcylindrical or compressed,
4 to 10 mm. in diameter, dividing at unequal intervals, often irregularly, occasion-
ally even anastomosing. Surface without monticules, but usually exhibiting well
marked substellate spots, consisting of aggregations of large, thick-walled cells, in
many cases surrounding a minutely granulose central space. Zocecial apertures
more or less oblique, the degree depending upon age, appearing thin-walled and
angular when in a good state of preservation, but much smaller and ovate, and
seemingly with much thicker walls, when slightly worn ; about twelve in 3 mm,
Mesopores wanting, acanthopores small, inconspicuous superficially. When per-
fectly preserved the walls are minutely granulose. ~

Internal characters: Tangential sections will present a variety of appearances
depending upon the age of the specimen sectioned, and the distance from the sur-
face. In the central or deeper parts of a section prepared from an old example
(plate XX, fig. 32), the zocecia have thin walls, each will have a well-defined cysti-
phragm, or, if too deep to show the end walls distinctly, will be crossed by three or
four straight and curved lines, representing both cystiphragms and diaphragms.
From this condition we pass gradually into stages in which the walls are thickened,
the cystiphragms filled up more or less completely and their ends drawn out
and around so as to enclose a comparatively small ovate open space. At the same
time the walls assume a minutely granular character, while at many of the angles
of junction a larger dark spot (acanthopore) is to be detected. These stages are
illustrated in figures 32 and 30. The lower half of the latter represents an unusual
condition, in having the original wall undefined. It should be remembered that very
few sections will show more than the first stage, and that, on account of the brevity
of the peripheral region and the obliquity of the zoccial tubes, it is at all times
rather difficult to prepare really satisfactory tangential sections.

Figures 29 and 31 illustrate vertical sections taken from fully matured examples,
the first from Canada, the second from Minnesota. These and other sections show
that the tubes bend outward very gradually ; that they are tabulated throughout,
with the diaphragms from one to three times their diameter apart in the axial region.
As they near the periphery the diaphragms become oblique and curved and then pass
over into series of cystiphragms and short, crowded diaphragms, with from twelve
BRYOZOA. 243

Homotrypa callosa.]

to sixteen of the latter in 1 mm. The most peculiar feature of the species, perhaps,
is the solid filling of the cystiphragms near the surface. This is, however, a pecu-
‘ liarity that is not shown to advantage except in sections of old examples.

Foord’s figures of this species (op. cit.) are not entirely satisfactory, though suffi-
ciently so to make the identity of the Minnesota examples referred to it a matter of
high probability. Still, in making the identification I relied chiefly upon the char-
acters of a Canadian example kindly furnished me by the author of the species.

The obliquity of the zocecial apertures, and the substellate surface spots will
serve to distinguish the species from associated forms, while its peculiar internal
structure separates it from all others known to me. The affinities of the species

are somewhat doubtful, but it is certainly not related very closely to H. obliqua
Ulrich, of the Cincinnati group. .

Formation and locality.—The types are from the Trenton limestone at Ottawa, Canada. In Minne-
sota the species is an abundant fossil in the Galena shales, in the upper beds especially, at several local-
ities in Goodhue county, and at St. Paul, Minnesota.

Mus. Reg. Nos. 7636, 8021, 8043, 8058.

*

Homotrypa CALLOSA, 7. Sp.

PLATE XX, FIGS. 15-21.

Zoarium irregularly ramose, less than 80 mm. high ; branches generally some-
what compressed, 6 to 12 mm. wide, 5 to 10 mm. thick. Surface with moderately
distinct clusters of large cells, sometimes raised into low monticules. Zocecial aper-
tures subangular, nearly or quite direct, enclosed by rather thick, ridge-shaped walls ;
thirteen or fourteen in 8mm. Mesopores wanting. Acanthopores small, inconspic-
uous superficially. :

Internal characters: Tn tangential sections the most striking features are (1) the
thickness and minute structure of the walls (see figs. 16 and 21) and (2) the com-
parative straightness of the inner edge of the cystiphragms. In the Minnesota
specimens the latter seem to project a little farther across the zocecial cavity, while
the walls are uniformly a little heavier and the zocecia sometimes a trifle larger
than in the Kentucky form.

In vertical sections the tubes bend outward gradually, and are tabulated through-
out, remotely and irregularly in the axial region, where only diaphragms occur, and
more crowded, also consisting chiefly of cystiphragms, in the peripheral region. On
plate XX, fig. 19 shows the character of the tubes near the center of the branch,
while figs. 17 and 18 illustrate their usual appearance in the outer fourth of the
diameter. In other parts of the same sections the short diaphragms crossing the
244 THE PALEONTOLOGY OF MINNESOTA.

[Prasopora.

tubes from the series of cystiphragms to the opposite wall, are still preserved almost
to the surface. That they are often wanting, as shown in the figures, is probably due
to imperfect preservation.

This species is clearly distinct from all the preceding. Its relations seem to be
with H. curvata of the Cincinnati group. Superficially it resembles Monticulipora
arborea Ulrich, a form that is associated with it not only in Minnesota but also in
Kentucky. That species is separated by its smaller cells and finely granulose walls.
Internally they are quite distinct.

Formation and locality.-Galena shales, near Cannon Falls, Minnesota; shales of the Trenton group
at Burgin and Frankfort, Kentucky.

®

Genus PRASOPORA, Nicholson and Ethridge, jun.

Prasopora, NICHOLSON and Eruripes, jun., 1877, Ann. and Mag. Nat. Hist., ser. 4, vol. xx, p. 38;
1879, NrcHoLson, Pal. Tab. Vorals, p. 324, and 1881, “‘Genus Monti-
culipora,” pp. 102 and 202; 1882, ULricu, Jour. Cin. Soc. Nat. Hist.,
vol. v, p. 153, and 1890, Geol. Surv. II1., vol. viii, p. 371; 1887, FoRRSTE,
Ball. Sci. Lab. Dennison Univ., vol. ii, p. 170. *

Zoaria forming conical, hemispheric, discoid or irregular masses; at other
times growing in thin expansions; usually free in the adult state, with a wrinkled
epithecal covering upon the lower concave or flat side. Zocecia] tubes prismatic or
cylindrical, thin-walled, partially separated from each other, occasionally completely
isolated by smaller angular mesopores, best seen in young specimens and thin trans-
verse sections, and perhaps always smaller and less readily distinguishable at the
surface of mature or old examples. Acanthopores usually present, but in most cases
neither numerous nor strong. Cystiphragms in all the zoccial tubes. Diaphragms
crowded in the mesopores,

Type: P. graye Nicholson and Ethridge.

This is one of the best characterized genera of paleozoic Bryozoa. The species
moreover are most of them common fossils and widely distributed, so that the genus
is also important in a geological sense. Most of the species are restricted to the
Trenton rocks, and only one, P. parmula Foerste, of the Clinton of Ohio, is as yet
known from strata above the top of the Lower Silurian.
BRYOZOA. O46

Prasopora simulatrix.}

PRASOPORA SIMULATRIX Ulrich.
PLATE XVI, FIGS, 1-10.

Prasopora simulatric UuRicn, 1886. Fourteenth Ann Rep. Geol. Nat. Hist. Surv. Minn., p, 85.

Zoarium discoid in the younger stages, becoming hemispheric or subconical with
age; occasionally the central part of the upper surface is drawn out, and in a few
imstances has been observed even to divide into two branch-like lobes. The last
conditions, as well as various other irregular developments, areto be considered as
abnormal. Base more or less concave, usually with a central cicatrix of attachment
beyond which it is covered with a concentrically striated and wrinkled epitheca.
Upper surface celluliferous. Hight of zoarium varying from 5 mm. or less to 50 mm.
or more; diameter from 10 to over 100 mm. Zocecia with direct, subcircular aper-
tures, thin walls, those of neighboring cells generally in contact except at the angles
of junction, the latter being occupied by angular mesopores of variable though usu-
ally small size. In the youngest specimens the zoccia are the roundest and the
interspaces, occupied by the mesopores, the widest, while in the oldest the opposite
conditions prevail. More or less conspicuous clusters of cells of larger size than
the average occur at intervals of nearly 4 mm., measuring from center to center.
Between these cells the mesopores are commonly more numerous than elsewhere,
and in nearly all cases constitute aggregations of variable extent and substellate
form. These aggregations are unusually large and conspicuous in the var. orientalis
to be mentioned presently. In many casés, chiefly old examples, the mesopores
between the zocecia occupying the intermacular spaces might be overlooked,
although, as shown by thin sections, they are really numerous even there. Diam-
eter of an ordinary zocecium about 0.25 mm., with an average of eleven in 3 mm.
Those forming the clusters vary in size, generally, from 0.25.to 0.88 mm., but in the
var. orientalis a few in each may attain a diameter of 0.48 mm. Acanthopores
wanting. .

Internal characters: These, as shown in over one hundred thin sections, are
very constant in all the essential parts. In tangential sections the form of the
zocecial tubes varies from perfectly circular to polygonal, their walls in most cases
being very thin, and the cavity of each intersected by the crescentic edges of one or
more cystiphragms. The opening left by the cystiphragms is generally lateral and
of bi-convex shape, occasionally it is subcentrally situated and oval, but more com-
monly two or more cystiphragms combine to give it a subtriangular form. An
abnormality is sometimes met with in the confluence of two zocecia (see lower right-
hand corner of fig. 9). The zocecia are in contact with each other only in part
246 THE PALEONTOLOGY OF MINNESOTA.

LPrasopora.

perhaps only at limited points, the interspaces left between them being occupied by
’ the small mesopores. These vary somewhat in number, and more so in size, but are
always decidedly angular. At intervals they are collected into substellate macule
of greater or less extent, and in the immediate vicinity of these the zowcia are of
appreciably larger size than elsewhere. No evidence whatever of acanthopores has
been detected. :

In vertical sections the cystiphragms form continuous series on one or both
sides of the tubes, according as they extended all around the circumference or
embraced only a portion of same, while an equal number of straight diaphragms
crosses the remaining portion of the tube. In the Kentucky, Tennessee, and
Minnesota form of the species the tabulation of the tubes is more uniform and
crowded than in the Canadian and New York variety, for which the name
orientalis is proposed. In the former the cystiphragms average sixteen or seven-
teen in 2 mm., while in the latter the average does not exceed thirteen, and in
some cases is not over ten in that space. In the mesopores the diaphragms are
simple, and average about eighteen in 1 mm. for the typical form, and twelve for
var. orientalis.

Variety ORIENTALIS, ”. var.
PLATE XVI, FIGS. 1,2, 6, 7.

Monticulipora;(Diplotrypa) whiteavesi (part.) Nichglson, 1879. Pal. Tab. Corals, p. 316.

This subordinate name is proposed for the eastern variety of the species. It is
distinguished from the typical form by the greater extent and distinctness of the
substellate macule, the greater size attained by the zocecia in the immediate
vicinity of the maculze and the less compact tabulation of the zocecia and the
mesopores.

This species may really be the one referred to by Vanuxem in 1842 (Geol. 3d
Dist. N. Y. p. 46), when he speaks of “The Puffball favosite (Favosites lycopodites)’’
as being highly characteristic and in great numbers in the Trenton limestone of
New York. He adds, “it is found also in the lower part of the Utica slate, where it
ends,” and that “it is equally abundant at Frankfort, Kentucky, where it received
the name of Trianisites cliffordi.”

The name Favosites or Chetetes lycoperdon (equivalent to Vanuxem’s Favosites
lycopodites) is generally credited to Say, but no description of the form was ever
published by him, and the first known of the so-called species under that name is
Prasopora.] BRYOZOA, 247
found in vol. i, Pal. N. Y., 1847, in which Hall devotes nearly two plates to the
illustration of its supposed variability. I might point out some of the now only too
evident incongruities in the assemblage of forms so placed by that even then experi-
enced observer, but it would be more than useless, since, if such a name has any
claim whatever to stand, we must go back to Vanuxem’s lycopodites, because it has
priority not only of publication but also in the matter of illustration,

Professor H. A. Nicholson has given his views on the value of these equivalent
names in his work on “The Genus Monticulipora,” p. 8, 1881, and as my own conclu-
sions on the points at issue agree thoroughly with his I cannot do better than quote
his excellent statement of the facts: “My object in mentioning this in this place is
twofold. On the one hand, there are few corals which have been more commonly
quoted by American geologists and paleontologists than Chetetes lycoperdon Say, or
Cheetetes lycopodites Vanuxem ; and it would therefore be very desirable to establish,
if possible, the precise nature and characters of the form to be understood by this
name, though I am not aware that this has ever been satisfactorily accomplished.
On the other hand, I wish to record the opinion that the generally laudable desire of
preserving an old name, where this is possible; may sometimes be carried too far,
and that this is, in my view, an instance in point. No definition of Chetetes lycopod-
ites Vanuxem, which can be regarded as in‘any sense a definition, was given by its
original author, or has since been supplied by any subsequent observer, while it is
certain that this name (or the equivalent C. lycoperdon Say) has been applied by
different writers to wholly different forms.’ ‘“ Nor, in the case of a genus like Mon-
ticulipora, where external form goes for so little, can Vanuxem’s original figure,
however good, be regarded as satisfactory proof as to the species upon which he
really founded the name in question. Under these circumstances, therefore, I
think as I think about such names as Favosites fibrosa Goldf., and various other
similar titles, that it would bea real gain to science if there could be a general
agreement that designations of this kind—published, in the first place, with wholly
insufficient definitions, and subsequently employed by others in widely different
senses—should be dropped altogether, and that no attempt should be made to
revive them.”

To show the inadequacy of Vanuxem’s figure, which shows absolutely nothing
beyond the tubular structure of a hemispheric bryozoan mass,-I have drawn the
accompanying illustrations of the internal structure of four hemispheric species,
all of them from the Trenton and supplementing those figured on plates XVI and

XVII.

 

 

*T should like to add here that it would not be difficult. to show that since 1842 no less than one hundred distin-
guishable froms have been included under this indefinite general designation. E.0O.U,
248 THE PALEONTOLOGY OF MINNESOTA.

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Fie. 15. aand b. vertical and transverse sections of Prasopora selwyni Nicholson, Trenton limestone,
Ottawa, Canada; c and d, similar sections of Prasopora oculata Foord, Galena shales, near Cannon Falls,
Minnesota; e and /f similar sections of Mesotrypa quebecensis Ami, sp., Trenton limestone, Little Falls,
N. Y.; g and h, similar sections of Mesotrypa whiteavesi Nicholson, sp., Trenton limestone, Ottawa, Can.
All the figures are x18.

Indeed, there are at least ten hemispheric species, to any one of which the orig-
nal of Vanuxem’s figure might have belonged. Most of these are species of Prasopora
and Mesotrypa, but I do not in the least doubt that Vanuxem, as well as all the other
early workers in geology, would have included under one specific name, and perhaps
did, also species of Leptotrypa, Monotrypa, and even Crepipora, having a similar mode
of growth. In the absence of his illustrated specimen, and the utter impossibility of
deciding permanently to which of these various forms it belonged, it seems to me
not only desirable but necessary to drop the names lycopodites and lycoperdon, so far
as their application to fossils of the types in question is concerned.

Formation and locality.-The typical form of the species is one of the most abundant and character-
istic fossils of the shaly part of the Trenton group of central Kentucky. It occurs also at Nashville,
Tennessee, and in the Galena limestone at Neenah and Oshkosh, Wisconsin, and Decorah, Iowa. In
Minnesota it is abundant in the upper third of the Trenton shales at St. Paul, and rather rarely at other
localities in the state. Also in the upper part of the Galena shales at Kenyon and other points in
Goodhue county. The exact horizon of certain specimens in the state collection labeled Minneapolis,
Lanesboro and Mantorville, is somewhat doubtful. The variety orientalis is common in the Trenton lime-
stone at Ottawa, Peterboro, and other localities in Canada, and at Trenton Falls, New York.

Mus Reg. Nos. 4041, 5124, 5532, 5986-5988, 6786, 7570, 7571.
BRYOZOA. 249

Prasopora contigua.|

Prasopora contiaua Ulrich.
PLATE XVI, FIGS. 24-26

Prasopora contigua ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 87.

Zoarium hemispheric, base flat or slightly concave, usually less than 30 mm. in
diameter. Zocecia with very thin walls and polygonal apertures, ten or eleven of
the average size in 8mm. Clusters of zocecia, some of them attaining a diameter
of 0.37 mm., occur at intervals of a little less than.4 mm. Mesopores comparatively
few, often difficult to detect at the surface.

Internal structure: Tangential sections show that the zocecial walls are polygonal
and very thin, with neighboring cells in contact, except at many of the angles of
junction, these being occupied by one or two small mesopores. The latter often
form very inconspicuous clusters at the center of the groups of large zocecia, but
in the intermediate spaces not over half of the angles of junction between the
ordinary zocecia are occupied by mesopores. A few very small acanthopores are
developed. The opening left by the cystiphragms is generally.of ovate form and
more often eccentric than central in its position within the tube cavity.

Vertical sections are peculiar chiefly because they exhibit a marked decrease in
the number of mesopores when compared with other species of the genus.

This form is closely related to P. simulatriz, and perhaps should be classed as a
variety of that species. The distinguishing features are (1) the much smaller num-
ber of mesopores, (2) thinner walls, (3) the presence of small acanthopores, and (4) a
somewhat greater crowding of the cystiphragms, these averaging over twenty in
2mm. More specimens are necessary before the constancy, and, therefore, value, of
these differences can be established fully. The same species, very slightly modified,
occurs at Cincinnati, Ohio, about three hundred feet above the Ohio river bed.

Formation and locality—The Minnesota specimens are believed to have been found either in the
upper part of the Trenton shales or in the Galena shales, at localities in Goodhue and Dakota counties.

Mus. Reg. Nos. 5301, 5534, 5989.

Prasopora conorpEA Ulrich.
= PLATE XVI, FIGS. 11-15.
Prasopora noida Uxricy, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 87.
Zoarium generally depressed-conical, with the hight a little more than half the
diameter ; at other times subhemispherical; hight varying from 4 to 16 mm., the

diameter from 8 to 20 mm. Under snrface rather deeply concave, wrinkled concen-
trically, with a small central scar. Upper surface celluliferous and presenting, at
250 THE PALEONTOLOGY OF MINNESOTA. ‘

[Prasopora selwyni.

intervals of about 3 mm., more or less prominent monticules, whose summits usually
appear subsolid or minutely pitted ; their slopes are occupied by zocecia above the
average in size. Zocecial apertures subcircular, eleven or twelve of those of the
ordinary size in 8mm. Mesopores abundant, in most cases readily distinguishable
at the surface with the aid of a good lens. Acanthopores small, inconspicuous.

Internal characters: These require no detailed description, being brought out
sufficiently in figs. 14 and 15. Compared with those of P. simulatrix Ulrich, we find
that the zocecial walls are thinner, the mesopores rather more abundant, and that
small acanthopores, one or more to each zoccium, are present, these structures being
absent in P. simulatriz, The tabulation of both sets of tubes is also more compact,
the average number of diaphragms in the mesopores in 1 mm. being about thirty,
and the cystiphragms in the zocecial tubes over twenty-five in 2mm. In the latter
respect the species is nearer P. contigua Ulrich, from which it is distinguished by its
smaller size, more conical form, tuberculated surface, and more numerous mesopores.
More than five hundred specimens show that the subconical form, more or less
developed monticules, the strongly concave base, and the small size of the zoarium
are persistent characters, suflicing to distinguish the species almost at a glance from
other forms of the genus,

Formation and locality.—Restricted to the upper third of the Trenton shales, occurring rather
rarely at St. Paul, but more abundantly at several localities in Goodhue county. The best locality is at
Oxford Mills, near Cannon Falls.

Mus. Reg. Nos. 3483, 7622, 8024, 8037.

Prasopora sELwyni Nicholson.
PLATE XVI, FIGS. 16-17.

Monticulipora (Diplotrypa) whiteavesii (part.) NICHOLSON, 1879. Pal: Tab. Corals, p. 316.
Monticulipora (Prasopora) selwynit NICHOLSON, 1881. ‘‘The Genus Monticulipora,” p. 206.

Zoarium discoid, subconical, or hemispheric, rarely more than 30 mm. high, and
in most cases varying between 40 and 90 mm. in diameter. Base flat or gently con-
cave, the epithecal plate striated or wrinkled concentrically. Surface characters of
the Minnesota specimens obliterated through weathering, the only one still distin-
guishable being the substellate macule. Their specific characters, however, are
clearly determinable by means of thin sections.

Tangential sections are not materially different from those of P. simulatrix
Ulrich. As a rule the zocecial walls are a little thinner, and the mesopores of larger
size. But vertical sections, as may be seen by comparing figs. 1 to 5 with 16 on plate
XVI, are quite different. The tabulation of the tubes is on the whole less compact,
BRYOZOA. 951

‘ Z
Prasopora, insularis.]

but the principal peculiarity is found in the cystiphragms, these appearing as series
of semicircular lines, each distinct from the other, on one or both sides of the zocecial
tubes. In the latter case they are arranged alternately. About three cystiphragms
occur on each side in 1 mm., while in the same distance six or seven diaphragms
cross the space left by them. This is the usual arrangement of the cystiphragms,
but’ in many of the tubes they also form loose connecting series very much as in
P. similatrix, var. orientalls (see plate XVI, fig. 2).

This species is certainly distinct from P. simulatrix, the isolated condition of
the cystiphragms being too striking a feature to be considered as less than specific.
Foord’s P. affinis and P. oculata, the first especially, are closer relatives, having like-
wise the cystiphragms isolated and not forming continuous series. The first, a
smaller species, with no macule, and conical instead of semicircular cystiphragms,
is known as yet only from Canada.* P. oculata, however, has been found in Minne-
sota, and is described on a succeeding page.

Formation and locality.—Dr. Nicholson’s types of the species are from the Trenton limestone of
Peterboro’, Ontario. Foord says the species “is very abundant throughout the Trenton formation of
Canada.” Also that it has been found in the upper beds of the Chazy, at Nepean, near Ottawa. The
Minnesota specimens were collected by the author in the upper part of the Galena shales near Cannon
Falls. It is there associated with Monticulipora grandis Ulrich, another massive but more irregularly
growing form, that was at first believed to be restricted to the top of the lower limestone.

PRASOPORA INSULARIS, 1. Sp.

PLATE XVI, FIGS, 18-23.

Zoarium small, discoid, plano- or concavo-convex, commonly from 15 to 20 mm.
in diameter and 5 or 6 mm. in hight. In a very large example these dimensions are
respectively 28 and 12 mm., while in the smallest seen they are 1.5 and 0.5 mm.
Under surface with a central scar, and beyond it delicate radiating lines, fine con-
centric strie, and, at intervals indicating stages of growth, stronger wrinkles. Very
often the zoaria are evidently made up of distinct superimposed layers, but these are
not usually distinguishable internally. Upper or convex surface without monticules,
but exhibiting, at intervals of about 4 mm., distinct clusters of large zoccia. Gen-
erally, at the center of each of these clusters, the mesopores which are small and in
nearly all cases just about numorous enough to isolate the zovecia, are gathered into
groups of varying size. Zocecial apertures circular, those in the clusters attaining a
diameter of 0.4 mm., while those of the smaller size in the inter-macular spaces
average about 0.22 mm., with eleven or twelve in 3 mm.

anaes ‘ imens of P. afinis were collected near Cannon Falls in the upper part of the
*Since writing this a number of spec c
Gates ohales, associated with species of Nematopora and Arthroclema armatum.
252 THE PALEONTOLOGY OF MINNESOTA.

(Prasopora oculata.

Internal characters: The first peculiarity to be noticed in tangential sections is
the relatively great abundance of the mesopores. In most specimens they form a
complete ring around the zocecia, and it is chiefly the large cells in the clusters that
are occasionally in contact at limited points. The zocecial walls are thin, and in
one section have the peculiar tubular structure shown in fig. 21. The cystiphragms
are more numerous and extend to a less distance from the walls than in any other
American species. The opening left by them is of various shapes, generally sub-
angular, and often removed from the walls. True acanthopores have not been
detected. :

In vertical sections the abundance of the mesopores, the narrowness of the
cystiphragms, and the unusual crowding of the tabulation in both sets of tubes,
are the distinctive features. In the mesopores the average number of diaphragms
in 1 mm. is over twenty-five, while the cystiphragms may number as high as twenty
in 1 mm., though the average is not likely to be over fifteen in that space.

Figures 18 and 19 represent one of two examples that may prove distinct.” In
tangential sections it differs in the greater size of the mesopores, and in the different
appearance of the cystiphragms. In vertical sections the cystiphragms are less
crowded and extend farther inward, while the mesopores here and there change
into vesicles, a peculiarity that has not been observed in the usual form of the
species. Provisionally the doubtful form may be distinguished as var. filmorensis.

This species is readily recognized by its small size and discoid shape. When
studied by means of thin sections it cannot be confounded with any other known
to me. °

Formation and locality.—This is probably the commonest and most characteristic fossil of the
Galena shales, having been found in greater or less abundance at nearly every locality in the state
where that horizon is known to be exposed. The species also occurs in the Galena at the quarries near
Neenah, Wisconsin, and at Decorah, Iowa. Var. filmorensis seems to have come from a lower horizon at
Fountain and Preston, both in Fillmore county.

Mus. Reg. Nos. 310, 5991, 5992, 7569, 7601, 7611, 7628, 7637, 7644, 7666, 8057; var. filmorensis, 5990.

Prasopora ocunata Foord. j
FIG. 15, ¢, d, PAGE 248.

Prasopora oculata FoorD, 1883. Contri. Micro-Pal. Cambro-Sil. Rocks, Can., p. 11.

Zoarium a thin, discoidal expansion, 15 to 30 mm. in diameter, and from 1 to 3
mm. in thickness. Of the Minnesota examples none is thicker than 2 mm., and all
are nearly 25 mm. in diameter. Under surface flat or gently concave, and marked
with more or less strong wrinkles of growth, and sometimes with very fine radiating
lines. Upper surface celluliferous, exhibiting subsolid maculz (clusters of mesopores)-
BRYOZOA. ‘ 253

Prasopora lenticularis.]

at intervals of about 3 mm., each a mm. or more in diameter. Surrounding these
the surface is depressed to a variable degree, and occupied by angular zocecial
apertures of comparatively large size and very few mesopores. The average diam-
eter of these zocecia is about 0.28 mm. On the rounded ridges between the depres-
sions the zocecial apertures are circular and smaller, averaging about 0.2 mm. in
diameter ; here they are also completely surrounded by a row of small mesopores.

- Internal characters: The tangential section figured on page 248 shows in the
upper half one of the macule with the large zocecia surrounding it and occupying
the depressed hexagonal surface spaces. Between these zocecia the mesopores are
very few, but farther out, in spaces representing the ridges (lower third of figure),
the mesopores usually completely isolate the, here also smaller, zocecia from each

_ other. Acanthopores are wanting.

In vertical sections (fig. 15c) the maculz appear as numerous, small, subequal,
closely tabulated tubes. One or two similar mesopores occur between many of the
zocecia in the inter-macular spaces. In the zoccial tubes the transverse partitions
are quite different. The appearance of the cystiphragms depends upon the direction
in which the section passes through them. When this is at right angles they appear
(see the central tube of the three shown in the figure) as narrow loops projecting
inward from the walls. Sometimes a complete diaphragm passes between each pair.
A variety of appearances, some of them shown in the figure, result when the section
passes through the cystiphragms at other than a right angle.

This species is readily distinguished from its associate, P. insularis Ulrich, as well
as from all the other species of the genus known to me, by the division of the surface
into subhexagonal depressed spaces. The zoarium is also unusually thin, while the
internal structure is peculiar enough to be distinguished at once, even from its
nearest allies, P. affinis Foord, and P. selwyni Nicholson. Still, I am not fully satis-
fied that the form is in all cases to be distinguished specifically from P. affinis, small
specimens of which have recently been found associated with it.

Formation and locality.—Rather rare in the Galena shales at several localities in Goodhue county,
Minnesota. The types of the species are from the equivalent Trenton limestone at Ottawa, Canada.

Mus. Reg. No. 7625.

PRASOPORA LENTICULARIS, ”. sp.

PLATE XVII, FIGS. 22-25,

Zoarium small, lenticular, beginning its growth upon foreign bodies, as far as
observed, about 12 mm. in diameter and 1 mm. thick. Zocecial apertures regularly
arranged, oval, twelve or thirteen in 3 mm., each of the smaller or average size
0.18 by 0.23 mm. In the clusters a few of the largest may attain a siza of 0.35 by
254 THE PALEONTOLOGY OF MINNESOTA.
[Aspidopora.

0.28 mm. Zocecial walls very thin, in contact at limited points, yet leaving compar-

atively large and easily distinguished interspaces, which, because the prevailing

arrangement of the apertures is quincuncial, are commonly bounded by four concave

sides. In most cases each of these spaces is occupied by a single mesopore, averaging

0.1 mm. in width and a little more in length. Mesopores but little if at all more

numerous in the clusters than elsewhere. They may be however 4 little larger and.
less regular in shape. Acanthopores apparently wanting.

This species may be nearly related to P. simulatriz Ulrich, but it is not its
young. This is shown best by thin sections, but the smaller size and more oval
shape of the zocecial apertures, the absence of macule, and the larger size and dif-
ferent shape of the interspaces, alone are sufficient in discriminating between them.
Comparing internal characters these differences are emphasized, while another point
is added in the greater separation of the diaphragms in the mesopores. Tangential
sections are a little like those of P. insularis, var. filmorensis, but the zocecia in that
species are completely isolated, and the tabulation of both sets of tubes much more
crowded. It seems to me that Aspidopora parasitica Ulrich, is more closely related,
but differs sufficiently in its parasitic growth, more closely tabulated mesopores, and
in possessing small acanthopores.

Formation and locatity.—Rare in the upper third of the Trenton shales at St. Paul, Minnesota.

Genus ASPIDOPORA, Ulrich.
Aspidopora, ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 155; 1890, Geol. Sur. I11., vol. viii, p. 373.

Zoarium consisting of one, or two or more superimposed, thin expansions, each
1 mm. or less thick, rarely parasitic, generally free, with an epithecal covering on
the concave lower side ; typically composed, according to age, of from one to many
subequal parts, each gently convex, with the zocecia increasing in size from their
margins to near their centers. Mesopores numerous, largest and best seen exter-
nally in the younger stages. Acanthopores usually present, always small. : Dia-
phragms horizontal and closely set in the mesopores, usually wanting in the zocecial
tubes, but one or more cystiphragms occur in most of the latter.

Type: A. areolata Ulrich, Utica horizon, Cincinnati group.

This genus is so closely related to Prasopora, Nich. and Ethr., jr., that for some
time I have considered the propriety of dropping the name in favor of theirs. But,
as I could not arrive at a wholly satisfactory conclusion, it seemed best to retain the
genus till we can learn more of the developmental history of this section of the
Monticuliporide.
/ BRYOZOA. 255
Aspidopora.]

Taking Aspidopora in the sense above described, there is only one character
(the other peculiarities being dependent upon it) that will distinguish it from
Prasopora, namely, the thinness of the zoarial expansion and the consequent brevity
of the zoccial tubes. That this is the mature condition of the zoaria is proved by
finding hundreds of examples of some of the species, not one of which exceeds 1 mm.
in thickness, though many of them may be over 25 mm. in diameter. Some may
consist (see plate XVII, fig 17) of several layers in contact at limited points but
really quite distinct from each other, and thus showing that, beyond the develop-
ment of the individual layers, the method of growth is not the same as in Prasopora.
In that genus the tubes, though perhaps presenting many immature and mature re-
gions or layers, are continuous throught the zoarium, even if it be over 50 mm. in
thickness. The tabulation of the two sets of tubes is essentially the same in the
two genera, excepting that in Aspidopora it is altogether as in the immature regions
of a Prasopora.* Perhaps some significance is to be attached also to the fact that
only a few cystiphragms and no straight diaphragms occur in the zocecial tubes.

Seven species are referred to Aspidopora as now defined. The next described,
A. parasitica, is the oldest, and occurs in the lower and middle thirds of the Trenton
shales. This species is also one of the earliest known phases of the type of structure
_ that at this time was evidently being rapidly differentiated into true Prasopora and
Mesotrypa. Before we can fully understand the relations of these groups of species
to each other it is necessary to discover the more primitive forms that are. to
be expected in the Chazy. The second species, A. elegantula, occurs in the Galena
shales, and the five remaining, A. areolata Ulrich, A. newberryt Nicholson, sp., A. caly-
cula (James) Nich., sp., A. eccentrica James, sp., and an undescribed species, in the
lower two hundred feet of strata at Cincinnati, Ohio.

Asprpopora PARasitica Ulrich.
PLATE XVII, FIGS. 26-32.

Aspidopora parasitica (part.) ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 90.

Zoarium parasitically attached to shells, Streptelasma profundum Conrad, and
other foreign bodies, upon which it forms very thin, subcircular or irregular
patches, 10 to 20 mm. in diameter, and 0.5 mm. or less in thickness. Zocecial walls
very thin, apertures oval or circular, arranged in regular curved series around
groups of cells distinctly larger than the average ; eleven or twelve of the latter in

f cystiphragms because these structures
lications on this genus (lve. cit.) I did not mention the presence o

__ Mi provtoos povlle in the type species. My present opinion is that the supposed diaphragms figured by me for A. areo
i cit., vol, vi, p. 164), are really cystiphragms, in part incorrectly drawn, lata
256 THE PALEONTOLOGY OF MINNESOTA.
[Aspidopora.

3mm. Of these the average diameter is 0.2 mm. or a fraction more, but that of the
largest in the clusters is commonly about 0.8 mm., though of a few it may by 0.35
mm. Mesopores numerous, readily distinguishable even at the surface, not surround-
ing the zocecia entirely. Acanthopores very small and inconspicuous.

Internal characters: These are faithfully and amply illustrated on plate XVII
rendering a description unnecessary. :

In my original description of the species I included another which is now sepa-
rated as Mesotrypa (?) spinosa, While I still regard them as related forms, the result
of a study of larger and better collections is to show that the latter is more inti-
mately connected with Mesotrypa infida than with the form to which I propose to
restrict the use of the name A. parasitica. I found no difficulty in distinguishing
specimens of the two species after discovering that they were really distinct. In
the parasitica the thickness of the zoarium is constantly 0.5 mm. or less, the acan-
thopores very inconspicuous, and the mesopores readily determinable under a good
lens. In the spinosa, on the contrary, the zoarium may attain a thickness of over
2 mm., the mesopores are scarcely distinguishable at the surface, and the acantho-
pores strong. Among associated parasitic species there is another that the beginner
may find it troublesome to separate. This is the Atactoporella insueta, really a very
different species, with more numerous acanthopores and less regularly distributed
zocecial apertures. :

Formation and locality.—Rather rare in the lower and middle thirds of the Trenton shales at Minne-
apolis, St. Paul and Fountain, Minnesota.

Mus. Reg. Nos. 5994, 5995.

ASPIDOPORA ELEGANTULA, 7. sp.

PLATE XVII, FIGS. 18-21.

Zoarium a thin, concavo-convex expansion, 25 to 83 mm. in diameter, and 0.5
mm. or less in thickness; sometimes consisting of two or more of such layers grown
loosely over each other. Under surface concave, with a concentrically and radially
marked epithecal membrane. Upper or convex surface celluliferous. Zocecial aper-
tures ovate, their walls thin, in contact only at limited points, the interspaces
distinctly occupied by mesopores, all the parts nicely arranged around clusters of
large cells. The latter are 3 or 4mm. apart, and in most cases slightly elevated.
Average size of ordinary zocecial apertures about 0.18 mm, by 0.25 mm., with eleven
or twelve in 3 mm:; size of the largest in the clusters rarely exceeding 0.28 mm. by
0.37 mm. Acanthopores wanting.
ions BRYOZOA. 257
Internal characters: These are sufficiently illustrated on plate XVII, but it is well
to state that a few tubes in both vertical and tangential sections may show a single
cystiphragm at the bottom. Diaphragms are wanting, as are acanthopores also.
This beautiful bryozoan is a true Aspidopora, and is rather closely related to
A, newberryi Nicholson, sp., the only reliable or constant difference between them
being in the number of cystiphragms. In the present species these structures are so
few that they may appear to be wanting entirely, but in Nicholson’s species they
occur in every zocecial tube, numbering in each, according to age, from one to ten.
Several discoidal forms are to be found in che same beds with A. elegantula, but none
of them are sufficiently like it to render confusion probable.

Formation and loeality.—Rather rare in the Galena shales at St. Paul, and near Kenyon, Goodhue
county, Minnesota.

Mus, Reg. No, 8126.

Genus MESOTRYPA, n. gen.

Diplotrypa (part.) NICHOLSON, 1879, Pal. Tab. Cor., p. 312, and 1881, The Gen. Monticulipora, pp. 101
and 155,

Zoaria hemispheric, conical, or discoidal, generally free, with the lower surface
covered by an epitheca. Zocecial tubes prismatic or cylindrical, more or less sep-
arated from each other by angular mesopores; internally with oblique and some-
times funnel-shaped diaphragms, that often simulate and probably are to be regarded
as peculiarly modified cystipliragms. Mesopores becoming smaller with age, inter-
sected by numerous diaphragms. Acanthopores generally present, sometimes of
large size.

Type: Diplotrypa infida Ulrich.

This genus is established for a natural group of species heretofore referred,
erroneously, I believe, to Diplotrypa*. These species are D. regularis Foord, D. que-
becencis Ami, D. whiteavesi Nicholson, D. patella Ulrich, the type D. infida, and three
new species, M. discoidea, M. rotunda, and M. (?) spinosa. To these might be added the
Niagara D. milleri Ulrich, but as the position of that species is somewhat in doubt,
it had best be left as originally placed till an opportunity offers to rework the type
specimens. ‘

The affinities of the proposed genus are not with Diplotrypa but with Prasopora.
Indeed, for some time I considered the propriety of referring the group to Prasopora,
yet after mature reflection the erection of a new genus was decided upon as serving
the purposes of classification better than would have been done by extending the

limits of that genus.
*See part ii, Contri. Micro-Pal. Campbro-Sil. Rocks, Can., p. 32, 1890.

—-17
258 THE PALEONTOLOGY OF MINNESOTA.
[Mesotrypa.

Mesotrypa InFIDA Ulrich.
PLATE XVII, FIGS, 1-8.

Diplotrypa infida ULRICH, 1886, Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 88.

Zoarium discoid or subhemispheric, with the base flat or concave and partly
covered with a concentrically wrinkled epitheca ; or it may be parasitic and conform
with the shape of the body grown upon; hight or thickness from 2 to 7 mm., diame-
ter from 12 to 20mm. Zocecial apertures varying from polygonal to subcircular,
the shape depending upon the number and size of the mesopores. In some speci-
mens the latter are almost certain to be overlooked, the zowcia being angular and
seemingly in perfect contiguity (p]. XVII, fig. 8). In others they are large enough
to constitute an obvious external feature (fig. 7). The latter condition is to be
regarded as less mature than the former, since in it the acanthopores are scarcely
distinguishable, while they are readily made out where the mesopores are smallest.
At intervals of 3 or 4 mm. there are clusters of large zocecia varying in diameter
from the smaller or ordinary sizes of 0.2 to 0.24 mm. to 0.4 or 0.45 mm. An average
of eleven of the ordinary size in 8 mm. —

Internal structure: In vertical sections the tubes are everywhere perpendicular
to the basal membrance. Their walls are a little thicker than usual in species of
the genus. In the lower part of the zoarium the mesopores with their numerous
diaphragms are very conspicuous. In following them upward they seem to be re-
duced in diameter, permitting the zocecial tubes to come in contact with each other.
These zones may be repeated several times. Diaphragms are numerous though not
regularly distributed in the zocecial tubes. The appearances presented by them are
exceedingly variable. Some appear to be horizontal and straight or slightly bowed
down in the middle (figs. 4 and 6), others are obliquely curved and perhaps overlap-
ping (fig. 3), while still others are funnel-shaped (fig. 5). This variability however
is not a structural peculiarity, but is due to the varying angles at which the dia-
phragms are cut by the section.

Tangential sections vary according to the.depth from the surface at which they
divide the zoarium. In the immature region (fig. 2) we have rounded zocecia, almost
completely surrounded by mesopores, and small acanthopores. In the mature region
(fig. 1) the mesopores are much smaller, the zocecia somewhat larger and subangular,
and the acanthopores larger. In most of the zocecial cavities the oblique and some-
what funnel-shaped diaphragms are represented by curved lines, often closely sim-
ulating the appearances of ordinary cystiphragms.
Mesotrypa (?) spinosa.] BRYOZOA. 259

The mesopores are less numerous, and the tabulation of both sets of tubes more
crowded than in M. whiteavesi Nicholson, sp. In M. regularis Foord, sp., the dia-
phragms are few in the zocecial tubes. This is likewise true of M. quebecensis Ami, sp.,

in which acanthopores seem to be wanting entirely.

_Formation and locality.—In the middle third of the Trenton shales at Minneapolis, St. Paul and
localities in Goodhue and Fillmore counties, Minnesota.

Mus. Reg. No. 5993.

Mzsorrypa (?) SPINOSA, ”. sp.
-PLATE XVII, FIGS. 9-12.

Aspidopora parasitica (part.) ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 90.

Zoarium parasitic, 0.5 to 6.0 mm. thick. Zocecia small, circular, neatly arranged
about the clusters, twelve or thirteen of the ordinary size in 3mm. Interspaces or
walls rather thick, but the abundant mesopores shown in thin sections are rarely, if
ever, to be made out at the surface. This may be due in part to the large size and
prominence of the acanthopores. Internally, with crowded horizontal diaphragms in
the mesopores and mostly oblique curved partitions in the zoccial tubes. Sometimes
a few at the bottom of the tubes are precisely like ordinary cystiphragms (fig. 12).

This form seems to hold an intermediate position between M. infida and Aspi-
dopora parasitica, differing from the first in having smaller zocecia, thicker walls and
stronger acanthopores, and from the second in the greater thickness of the zoarium,
much stronger acanthopores, different tabulation of the zocecial tubes, and in but
rarely showing the mesopores at the surface, these being, so far as observed, always
distinctly visible at the surface of A. parasitica. Atactoporella insueta, another asso-
ciated parasitic species, has larger and less regularly distributed zocecia, with smaller
and more numerous acanthopores.

Formation and locality.x—Perhaps the commonest of the parasitic Bryozoa occurring in the middle
third of the Trenton shales at St. Paul, Minneapolis and other localities in Minnesota.

Mus. Reg. No. 8127.

MESOTRYPA QUEBECENSIS Ami, sp.

FIG. 15, ¢ and f, PAGE 248.
Diplotrypa quebecensis Ami, 1892. Canadian Record of Science, p. 101.

Zoarium discoid or subhemispheric, base gently concave, hight 4 to 20 mm.,
diameter 12 to 45 mm. At Decorah, Iowa, the specimens are generally about 25
diameter, and 6 or 7 mm. thick. The same is true of the Kentucky

mm, in
but in New York and Canada they are usually nearly again as large.

examples,
260 THE PALEONTOLOGY OF MINNESOTA.

[Mesotrypa quebecensis.

Mr. Ami’s original type is probably a young specimen, being only about 12 mm. in
diameter. Zocecial apertures rounded, the largest of those in the clusters attaining
a diameter of 0.4 to 0.45 mm., but those occupying the spaces between the clusters
average about 0.24 mm., with eleven or twelve in 3mm. Walls thin. Mesopores of
variable size, not isolating the zocecia, in most cases readily distinguishable at the
surface ; internally with diaphragms averaging about ten in 1] mm. Zocecial tubes
intersected by a few oblique curved diaphragms. These are developed chiefly in
zones, 3 or 4 mm. apart, in which several occur approximately on the same level in
all the tubes. In even these zones the diaphragms are separated but rarely by
intervals less than 0.5 mm., while between the zones they may be wanting for a
distance of 4 mm., though commonly occurring there at intervals of about 2 mm.
Not a sign of acanthopores has been detected on the surface nor in thin sections.

This species is closely related to M. regularis Foord, sp., differing therefrom
chiefly in wanting acanthopores. The same and other differences will be noticed
when thin sections'of it are compared with similar sections of M. infida, M. whiteavesi
and M. patella, in all of which the zoarium has very nearly the same shape. Young
examples are also very much like Prasopora insularis and P. lenticularis. Indeed, it
is a matter of no small difficulty to identify with certainty any of the host of dis-
coidal Bryozoa that are already known from Lower Silurian deposits without the
aid of intelligently prepared thin sections.

Formation and locality—Rather rare in the Galena Shales at Decorah, Iowa, in shales of the Tren-
ton group at Burgin and Danville, Kentucky, and in the Trenton limestone at Trenton Falls, New York.
Mr. Ami’s type is from rocks supposed to be equivalent at Quebec, Canada.

Mus. Reg. No. 8128.

MESOTRYPA DISCOIDEA. 7. sp.

 

 

 

 

 

 

 

et

 

Fie. 16. Mesotrypa discoidea Ulrich, upper beds of the Galena shales, Goodhue county, Minnesota.
Collection of E. O. Ulrich. Tangential and vertical sections, x 18, the latter consisting in part of two
distinct layers. :
Mesotrypa discoidea.] BRYOZOA. 261

Zoarium discoid, base flattened, upper surface gently convex; diameter, so far
as observed, less than 20 mm.; hight, sometimes divisible into two subequal layers,
4mm. or less. Upper surface with inconspicuous clusters of zocecia a little larger
than the average. Zocecial apertures rounded, rather regularly arranged, about
eleven in 3mm. Mesopores numerous, rather small, occupying merely the triangu-
lar or quadrangular interspaces left between the adjoining rounded zocecial walls.
The latter are very thin. As usual with species of this and related genera the
mesopores are more abundant (in this case completely isolating the zocecia) in the
basal or primitive,part of the zoarium than in the fully matured superficial portion.
Acanthopores apparently absent.

In vertical sections the chief peculiarity of the species is found in the tabulation
of the tubes. In both sets of tubes, namely, diaphragms are present in unusually
large numbers, there being a few more or less than thirty-five in 1 mm. in the meso-
pores, while in the zocecial tubes the average is eight or nine in the same distance.
In the latter the diaphragms, especially in the lower part, are frequently curved or
oblique, as shown in the figure, but some of the tubes have practically horizontal
diaphragms throughout. The mesopores are quite abundant at the curved basal
part of the zocecial tubes, becoming, however, very much less so soon after these
assume an erect position. Many of the zocecial walls may appear as completely in
contact, but the rule is that at intervals, at any rate, they separate, producing the
periodic tabulated swellings shown in the figure.

This species, having no acanthopores, belongs near M. quebecensis Ami, sp., from
which it differs strongly in vertical sections, the diaphragms being much fewer in
that species. M. rotunda, also without acanthopores, has more numerous and com-
paratively loosely tabulated mesopores.

Formation and locality—Rare in the uppper part of the Galena shales (Anastrophia beds) at local-
ities in Goodhue county, Minnesota.
262 THE PALEONTOLOGY OF MINNESOTA.

L[Mesotrypa (?) rotunda,

Mesorrypa (?) ROTUNDA, ”. Sp.

 

“ ¥re.17. Mesotrypa. rotunda Ulrich, upper beds of the Galena shales, Hader, Goodhue county, Min-
nesota. Collection of E.O. Ulrich. 1, tangential section showing arrangement of cells about one of the
clusters. The latter embraces several young zocecia. 2, another portion of same section, with half of a
cluster shown above. 3, vertical section passing through a cluster like the one represented in 1, and
showing at center of figure several mesopores that have enlarged and assumed the tabulation of zowcial
tubes. 4, another portion of same section showing a partial break in the continuity of the tubes, and
consequent irregularities in their tabulation. All x 18. :

Zoarium a small hemispheric mass, 10 mm. in diameter, 6 mm. high, and 4 mm.
thick at the middle, the under surface being strongly concave and wrinkled concen-
trically. Upper surface without monticules, but exhibiting fairly distinct clusters
of large cells, rendered in many cases more so by aggregations of mesopores. Zoce-
cial apertures rounded, about eleven of the average size in 3 mm. Mesopores
abundant, but seeming never to separate the zocecia completely. Acanthopores
wanting.

Internal structure as shown in the accompanying figures.

This form is distinguished from the other species of the genus in having all the
diaphragms essentially horizontal. This fact casts some doubt upon the propriety of
placing the species under Mesotrypa, and the uncertainty of the reference is empha-
sized by undoubted relations with species now classed as Diplotrypa (e. g. D. millert
Ulrich, and D. ? dubia Ulrich), having a decided leaning toward Callopora.

Formation and locality.—Lower beds of the Galena limestone at Hader, Goodhue county, Minnesota.
Batostomellidz.1 BRYOZOA. 263

Family BATOSTOMELLIDA, Ulrich.
Genus BYTHOPORA, Miller and Dyer.

Bythopora, MILLER and DyeEr, 1878, Contri. to Pal., pt, ii, p. 6; ULRrcu, 1890, Geol. Surv. IIl.,
vol. viii, p. 376.

Zoaria consisting of very slender branches. Zocecial apertures very small,
oblique, lanceolate, narrowing above. Interspaces variable, generally thick, often
channeled. Mesopores and diaphragms very few or wanting. Acanthopores usually
present, never numerous, rarely more than one to each zocecium.

Type: JB. fruticosa Miller and Dyer. Cincinnati group.

The two species found in Minnesota are very similar to the typical species, and,
although the latter is not as fully known as we would desire, there can be no reason-
able doubt that the three forms are thoroughly congeneric. At least five other
species occur in the rocks about Cincinnati, Ohio, but only two of these have been
described, both by Nicholson, one as Chetetes delicatulus, the other as Ptilodictya ?
arctipora. Still another form was described by me as B. striata from the upper beds
of the Hudson River group at Stony Mountain, Manitoba, and Middletown, Ohio.

BytHorora HERRICK! Ulrich,
PLATE XXVI, FIGS. 1-6.

Bythopora herricki ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 99.

Zoarium ramose, 20 to 40 mm. high, consisting of slender cylindrical branches,
0.8 to 2.0 mm, in diameter, dividing dichotomously at intervals of from 8 to 12 mm.
Zocecial apertures small, very oblique, narrow, rounded behind, drawn out in front ;
when perfect with a minutely granulose rim, highest posteriorly. Interspaces
depressed, wider than the apertures. In the worn condition in which the species is
often found, the ramulets appear to be made of thick-walled tubes with oblique
apertures. The arrangement of the apertures is in more or less irregular, longitud-
inal and diagonal rows, with four in 1 mm. in the latter. Acanthopores small, few,
but rarely preserved at the surface. True mesopores wanting.

Internal characters: A number of thin sections were prepared, but in all the
finer details of structure are more or less completely destroyed by crystallization.
The sections figured were prepared from an unusually old example. I have endeav-
ored to represent the characters shown in these as faithfully as possible, and as I
cannot add anything of importance not shown, it is unnecessary to attempt a

description of them.
264 THE PALEONTOLOGY OF MINNESOTA.
[Bythopora alcicornis.

The species is closely related to B. arctipora Nicholson, sp. of the Cincinnati
rocks, but the zocecial apertures are narrower and more produced anteriorly than in
that species.

Formation and locality.—Fragments of this species are common in the middle third of the Trenton
shales at St. Paul and Minneapolis, Minnesota. Good specimens, however, are rare.

Mus. Reg. Nos. 6012, 6013.

ByTHOPORA ALCICORNIS, ”. Sp. fe

PLATE XXVI, FIGS. 7-9.

In this species the zoarium divides at shorter intervals than in any other of the
genus known, the distance between the branches varying between the extremes of 1.5
to 6.0mm. Compared with B. herricki, we find that the average size of the branches
is a little less, that they bifurcate at shorter intervals, that the zocecial apertures are
arranged less regularly and on the whole less compactly, the direction of the rows
being interrupted and changed by meeting with spots, 2 or 3 mm. apart, in which
the interspaces between the apertures are much wider than elsewhere. These sub-
solid spots distinguish the species from all the others as well, excepting an unde-
scribed larger form occurring in the upper beds of the Hudson River group at
Waynesville, Ohio, in which they are of greater extent and constitute a very obvious
superficial character.

Formation and locality.—Upper third of the Trenton shales, associated with Phylloporina corticosa
and Prasopora conoidea, near Cannon Falls, Minnesota. :

Genus KRIDOTRYPA, n. gen.

4s

Batostomella (part.) ULRIcH, 1890. Ill. Geol. Sur., vol. viii, pp. 375, 432.

Zoaria ramose, branches slender. Zocecia more or less oblique, with thick walls,
the tubes intersected by diaphragms only. The latter may be wanting in the axial
region, are in most cases absent for a short distance within the apertural edge, but
always present and closest together in the turn from the axial into the narrow
peripheral region. Mesopores with close-set diaphragms, varying in number, some-
times abundant, at other times very few. Acanthopores small, never numerous,
sometimes wanting.

Type: Eridotrypa mutabilis, n. sp.

This genus became necessary partly through the restriction of Batostomella to
its Carboniferous types, and partly for the accommodation of a number of species

that could not be disposed of satisfactorily under any of the existing genera.* The

*It is unfortunate that both Hall’s recently proposed Trematella (Pal. N. Y., vol. vi, p. xiv,
should have been founded upon practically the same type of structure.
are now to go under Eridotrypa.

1887) and my Batostomella (1882)
In both cases species are included doubtfully that
Eridotrpya.] BRYOZOA. . 965

genus will include beside the following, probably two as yet undescribed species
from the Trenton of Kentucky, Batostomella simulatrix Ulrich, a widely distributed
species from the upper beds of the Hudson River group, Trematopora echinata Hall,
from the Niagara group of Indiana, T.? (Trematella 2) corticosa Hall (see Pal. N. Y.,
vol. vi, p. 15, pl. X, figs. 1-10), from the Lower Helderberg of New York, and Batosto-
mella obliqua Ulrich, from the Hamilton group of Michigan.

The systematic position of the genus, though in a measure doubtful, is probably
‘intermediate between Homotrypa (compare H. similis Foord) of the Monticuliporide,
and Bythopora, Miller and Dyer, of the Batostomellide. Because of the absence of
cystiphragms it will be best to embrace the genus provisionally in the latter family.

ERIDOTRYPA MUTABILIS, 1. Sp.

PLATE XXVI, FIGS. 20-82.

Zoarium ramose, dividing at rather long but irregular intervals; branches 2 to
6 mm. in diameter, the younger examples slender and nearly cylindrical, the old
ones more or less irregular. Considerably over half of the hundreds of specimens
seen are from 3.5 to 4.5 mm. in diameter. Zoccial apertures variable, the changes
due chiefly to age, always oblique, the degree decreasing with age; walls thick,
generally ridge-shaped and highest posteriorly, sloping gradually down into the
apertures. In young examples—also in old offes on which a new layer of zocecial
tubes was formed—the apertures may be exceedingly oblique and drawn out
anteriorly. With age they became gradually more direct. The arrangement of the
apertures is always more or less irregular, some of the short rows having six, others
seven, and occasionally eight in 2mm. Small macule, either pitted or irregularly
sculptured, commonly present in the older examples. In others the macule are
represented by clusters of zocecia which, though a little larger than the average, are
distinguished from them chiefly by the greater thickness of the interspaces. The
mesopores too are most variable. In some cases, but this is rare, they will appear to
be wanting over large portions of the surface (see fig. 24); in others they may be
twice as numerous as the zocecia. As a rule, however, they are to be counted as
few, appearing at the surface, except in rare instances, only as occasional shallow
depressions between the zocecial apertures. True acanthopores probably wanting,
but small knots at the angles of junction may be noticed.

Internal characters: These are, luckily, fairly constant in all essential features,
the principal variations observed being in the number of mesopores. Figs. 26 to 28
represent parts of sections prepared from an average example. Diaphragms occur
s

266 THE PALEONTOLOGY OF MINNESOTA.

(Eridotrypa mutabilis
all through the axial region at intervals, averaging about twice the diameter of a
tube. As the tubes are about to open at the surface the diaphragms increase in
number, and immediately thereafter the walls are greatly thickened, and mesopores
developed. The latter were unusually numerous in the sections drawn in figs.
31 and 32.

Variety MINOR, ”. var.

PLATE XXVI, FIGS. 20, 21, 29, 30.

This name may be attached to the small form represented by the figures cited.
The surface magnified is generally very much as shown in fig. 21, the zocecial walls
being thinner than in typical mutabilis. But the principal peculiarities are to be
found in the axial region, as shown in vertical sections. First, the central tubes are
unusually large and their walls more wavy than in typical mutabilis; second, the
tubes altogether seem to have been developed more regularly, and their width in the
peripheral region somewhat less; and third, diaphragms are wanting throughout
the greater part of the axial region. Under ordinary circumstances these differ-
ences would be considered as of specific value, but in this instance, knowing the
extreme variability of the species, I cannot credit them with more than subordinate
importance.

The smaller size of the branches, oblique zocecial apertures, and the thicker
walls or inter-apertural spaces, distmguish the species without much trouble from
associated species of Homotrypaand Callopora. Despite its variability, I have always
found it one of the easiest of the numerous Trenton species to identify off-hand.

Formation and locality.—Very common in the Galena shales at many localities in Goodhue, Dakota
and Ramsey counties in Minnesota; also at Decorah, Iowa, and in the Galena at Neenah and Oshkosh,
Wisconsin; in the shaly portion of the Trenton group at many points in central Kentucky; also at Nash-
ville, Tennessee, and Ottawa, Canada. Specimens referred to the var. minor are to be found also in the
upper third of the Trenton shales at St. Paul.

Mus. Reg. Nos. 5541, 6009, 7561, 7603, 7623-3, 8034, 8050, 8079.

ERIDOTRYPA EXIGUA, 1. Sp.,

PLATE XXVI, FIGS. 17-18,

Zoarium small, branches very slender, several hundred fragments varying in
diameter from 0.6 to 1.0 mm.; bifurcations apparently remote. Some of the frag-
ments are pointed at the lower end, indicating a free condition of the zoarium, or an
articulation like that of Escharopora. The eastern form of the species is usually a
little stronger than the average of the Minnesota types, the specimens seen from
BRYOZOA. 207
Eridotrypa exigua.]

Vermont and New York being mostly 1.0 mm. or a little more in diameter. Consid-
ering the small size of the branches, the zocecia are large. Their apertures are
oblique, but not excessively so, subequal, and arranged in both longitudinal and
diagonal series, the former with eight in 3 mm., predominating in the small speci-
mens, and the latter in the larger. At the lower end of each aperture the wall is
usually raised into a spine-like prominence. In vertical sections the greater part of
the branch is seen to consist of comparatively large and nearly or quite vertical tubes,
intersected here and there by a diaphragm. The peripheral region is exceedingly
short and abrupt.

The small size of the branches might be regarded as indicating Bythopora rather
than Eridotrypa, but the comparatively large zocecia and the internal characters, so
far as known, point to the last genus with considerable certainty. Considered spe-
cifically, its branches are so much smaller than those of even the var. minor of the
preceding species that there is really no likelihood of confusion here. Both Bytho-
pora herricki and B..alcicornis have smaller zocecial apertures and impressed, instead
of ridge-shaped, interspaces.

Formation and locality.—A large number of fragments were picked from washings of upper Galena
shales collected from a locality near Cannon Falls, Minnesota. The eastern fourm of the species occurs in
the Trenton limestone at Trenton Falls, New York, and Chimney Point, Vermont.

Mus. Rey. No. 8129.

Family HETEROTRYPIDA, Ulrich.
Genus HETEROTRYPA, Nicholson.

Heterotrypa (part.) NICHOLSON, 1879, Pal. Tab. Corals, p. 291; NICHOLSON, 1881, Genus Monticuli-
pora, pp. 101 and 103.

Heterotrypa, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist.. vol. v, p. 155; ULRICH, 1882, idem, vol. vi, p. 83;
FoorD, 1883, Contri. Micro-Pal. Cambro-Sil. Rocks, Can., p. 20;
Urricg, 1890, Geol. Surv. Ill., vol. viii, pp. 371 and 413.

Zoaria frondescent, subramose, or incrusting. Zocecial tubes prismatic, some-
times subcylindrical. Apertures angular, subcircular, or slightly petaloid. Walls
moderately thin. Mesopores varying in number, sometimes abundant, with illy-
defined walls. Acanthopores small, usually numerous. Diaphragms well developed,
generally horizontal ; occasionally a few may be concave or recurved.

Type: 4H. frondosa d’Orbigny, sp., (H. mammulata Nicholson, not d’Orbigny).

This genus is not yet known to occur in the rocks of Minnesota, but the two
species following are to be looked for in the southern part of the state, being rather
common fossils in the Hudson River rocks of Illinois and Wisconsin,

For remarks on this genus see under Dekayella,
268 THE PALEONTOLOGY OF MINNESOTA.
[Heterotrpya prolifica.

Hersrotrypa prouiFica Ulrich,
(Not Figured.)

Heterotrypa prolifica ULRIOH, 1890. Geol. Surv. Ill., vol. viii, p. 418, pl. xxxvii, fig. 1-Id.

Original description: “Zoarium frondescent, or subramose with much flattened
branches ranging in thickness from 4 to 12 mm., and at times attaining a hight of
10cm. Low rounded tuberosities arranged in irregularly intersecting lines, and
composed of cells a little larger than the average, commonly surrounding a cluster
of mesopores, serve to break up the monotony of an otherwise smooth surface.
Zocecial tubes curving in the axial region, direct throughout the peripheral region,
where their walls become considerably thickened. Zocecial apertures subpolygonal,
about eight in 2 mm., and 0.15 to 0.18 mm in diameter. Interspaces occupied by
calcareous matter; where very wide by a few mesopores with illy-defined walls.
Most of the mesopores are found in the clusters.

A few diaphragms in’ the axial region; in the transition period they become
more numerous; in the cortical region they are close set, a tube diameter or less
apart. In the outer portion of this region they are often concave, sometimes tend-
ing to the infundibular form. Mesopores more closely tabulated than the zocecial
tubes. Acanthopores a little more than one-third as numerous as the zocecia ; when
not situated at the angles, generally inflecting the zocecial cavity a little.”

“This species approaches quite closely to H. frondosa d’Orb., having a somewhat
similar growth ; but in that species the zocecia are more angular, the walls thinner,
mesopores far more numerous, and the acanthopores rather more abundant.”

Formation and locality—A common form in the upper beds of the Hudson river group at many
localities in Ohio and Indiana, also at Wilmington, Illinois, and Iron Ridge, Wisconsin.

HETEROTRYPA SINGULARIS Ulrich.
(Not Figured.)

Heterotrypa singularis ULRICH, 1890. Geol. Surv. IIL, vol. viii, p. 415, pl. xxxvii, figs. 3-3e.

Original description: “Zoarium subramose, at times attaining a thickness of 7
em. Surface smooth or nearly so, with, clusters of cell apertures a little larger than
the average. Zocecia about nine in 2 mm., angular and thin-walled in the axial,
subcircular in the mature region. There are commonly two or more successions of
immature and mature regions. Mesopores of variable size, very numerous, usually
angular or subcircular. Diaphragms developed very irregularly, at times but few

,
. BRYOZOA. 269
Dekayella.]

in the cortical region and wanting in the axial, at other times about two tube diam-
eters apart in the axial and close-set in the peripheral region. They are commonly
horizontal, often concave, sometimes infundibular and occasionally simulate cysti-
phragms if they are not of that nature. Acanthopores very numerous, inflecting
the viscerial cavity so as to give it a petaloid appearance.

“The extremely large size of this species, the remarkable development of acan-
thopores and mesopores and irregular character of the diaphragms are its leading
features. Some points of its structure leave me in doubt as to this being its rightful
position, but for the present it seems best to place it with Heterotrypa.”

Formation and locality.—U pper beds of the Hudson river group at Wilmington, Illinois, and Iron
Ridge, Wisconsin.

Genus DEKAYELLA, Ulrich.

Dekayella, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p..155, and vol. vi, p. 90; 1890, Geol. Surv.
Tll., vol. viii, p. 372.

Zoaria ramose, branches cylindrical or compressed. Zocecia angular or rounded,
the shape depending upon the number and disposition of the mesopores. Typically,
the mesopores are more or less numerously distributed among the zoccia, and
aggregated into irregular clusters. In other cases they may be wanting, except in
the clusters, while in some of the earliest forms they are so few as to be practically
absent. Acanthopores of two sizes, the large ones, equivalent to those of Dekayia,
commence in the axial region, the smaller ones more abundant and developed in
the peripheral region only. Diaphragms horizontal, numerous.

Type: D. obscura Ulrich, Utica horizon of the Cincinnati group.

This genus includes, so far as known, the earliest types of the family Heterotry-
pide. In the Trenton or more strictly speaking, the Birdseye shales of Minnesota
we have, besides species or varieties that are as typical of Dekayella as any occurring
in the Cincinnati rocks, two forms that, in having very few mesopores, are more
nearly like Dekayza, Edwards and Haime. Tangential sections of the one (Dekayella
prenuntia var. echinata) very much resemble those of Dekayia aspera Ed. and H., yet
when carefully examined, two sets of acanthopores—the one large, the other small—
will be noticed. The abundant tabulation of the tubes is also indicative of Dekayella.
The other form (D. prenuntia var. simplex) is, as the name implies, of a more simple
and perhaps the primitive type, with the acanthopores much smaller and scarcely, if
at all, separable into two sets.

The relations existing between Dekayella, Dekayia and Heterotrypa are so intim-
ate that I have seriously considered the propriety of throwing them together as one
270 THE PALEONTOLOGY OF MINNESOTA.
(Dekayella.

genus. The chief reason for doing so is that with the great abundance of material
—specific, varietal and individual—studied, an almost complete chain may be made
out connecting one with the other. But, as I have had occasion to state more than
once heretofore (ante pp. 115, 188, 216), this is not a sufficient reason for uniting two
or more genera. The groups of species embraced in each are natural and in a great
measure readily distinguished, and therefore must always be recognized in some
manner. Heterotrypa, as restricted and used by me, includes only frondescent or
palmate zoaria, with all the acanthopores small and approximately of one size;
Dekayia, subcylindrical or flattened stems growing from a large base, with one set
of acanthopores, mesopores very few or wanting, and few diaphragms in the tubes;
and Dekayella, zoaria as in Dekayia, but with acanthopores of two sizes, mesopores
more or less numerous, and abundantly tabulated tubes.

DEKAYELLA PRENUNTIA, ”. sp.; and VARIETIES.
PLATE XXIII, FIGS. 32-47, es

Compare Heterotrypa ulrichit NICHOLSON, 1881, ‘‘Genus Monticulipora,” p. 181.

Typical form: Plate XXIII, fig. 43,

Zoarium ramose ; branches subcylindrical, often compressed, dividing at irregu-
lar intervals, varying in diameter or width from 4 to 12 mm. Surface without
monticules, but in well-preserved specimens minutely spinulose ; clusters of large
cells inconspicuous. Zocecial apertures obscurely angular or rounded, enclosed by
moderately thin walls, averaging about thirteen in 8 mm. Mesopores not very
numerous, generally one to each zocecium, rather irregularly distributed, often
forming small clusters. Acanthopores small, about half-the number of zocecia.

Internal characters: In vertical sections the tubes are nearly vertical in the
axial region, and here are crossed by diaphragms at intervals equalling two to four
times their diameter. As the tubes bend outward an occasional acanthopore may
be detected, while the intervals between the diaphragms become less, until in the
fully matured peripheral region, in which the tubes are directed nearly at right
angles to the surface, the average distance between them is about one-half their
diameter. It is in the latter region that the mesopores are developed. These are
distinguished by their smaller size and more crowded diaphragms. An obscurely
beaded wall-structure, as shown in fig. 40, with overlapping diaphragms, is of com-
mon occurrence. :

Tangential sections show that the zocecia are mostly oval or rounded, their walls
of variable thickness, and in part separated by intervening mesopores. The latter
271
Dekayella prenuntia.] BEYOLOA,

vary considerably both in number and size, with medium conditions about as in
fig. 43. Acanthopores comparatively small, the principal set comparing in number
with the zocecia about as one is to four ; small set very minute, not often preserved,
at any rate, only rarely distinguishable in sections.

Mus. Reg. Nos. 6019, 6020, 8073, 8305.

Var. SIMPLEX, 7”. var. -

PLATE XXIII, FIGS, 39-42.

In this form the mesopores are reduced numerically to a minimum. Indeed,
they are not distinguishable externally, and only a very few are to be made out in
tangential sections. The zocecial apertures are polygonal and unusually regular in
their arrangement. The walls, too, get to be stronger than in any other form of the
genus, with perhaps one exception, while the acanthopores are, if not smaller, at any
rate less noticeable in thin sections. From an external examination merely speci-
mens of this species might be regarded, and with good reason, as belonging to the
Amplexoporide. Certainly they would scarcely be suspected of being closely related
- to Dekayella prenuntia. But with the aid of thin sections, vertical ones especially,
the true affinities of the form become obvious at once. Excepting that mesopores
are practically wanting, there is little or no difference between vertical sections of
the typical form of the species and var. simplex.

Mus. Reg. No. 8307.

Var. NZEVIGERA, n. var.
(Not Figured.)
This form differs from the preceding in having thinner zocecial walls, and clus-
ters of from five to thirty mesopores at the center of the usual groups of large
zocecia. In the var. simplex the zoarium consists generally of but few branches, but

in the best examples of the-present form they are numerous, strong and divide and
inosculate freely, the whole forming a mass over 70 mm. in diameter.

Mus. Reg. Nos. 6018, 7669.

Var. ECHINATA, ”. var.
PLATE XXIII. FIGS. 32-38,
This variety grows in large compressed branches, that seem never to inosculate,

The clusters of large cells are moderately distinct, and frequently enclose small
aggregations of mesopores. In having very few mesopores their structure agrees
272 THE PALEONTOLOGY OF MINNESOTA.

[Dekayella pranuntia.

with the two varieties immediately preceding, but specimens are distinguished at
once by the much greater size of the acanthopores, these being so large and prom-
inent that they are easily seen by the unassisted eye. An average distance of 0.5 mm.
separates them. Internally the walls vary in thickness, very commonly even in the
same tangential section. Where they are thinnest the acanthopores are the most
distinct, and it is chiefly in such parts that the small set is determinable. Aside
from the latter the general appearance of tangential sections is decidedly like that
of typical Dekayia.

Mus. Reg. Nos. 6016, 7657, 8022, 8098.

Var. MULTIPORA, ”. var.

PLATE XXIII, FIGS. 44-47.

In this form the acanthopores are likewise very large and, as a rule, are to be
geen with the naked eye on the surface of all well preserved specimens. Still there is,
as may be seen by comparing figs. 44 and 45, considerable variation in their size, so
that the identification of the variety depends chiefly upon the unusually numerous
and large mesopores and the rounded shape of the zocecia. In many cases, however,
it is difficult to discriminate positively between the two sets of tubes, as these are
shown in tangential sections. As a rule—perhaps the test is reliable at all times—
the zocecia never have any part of their walls convex upon the inner side. In
vertical sections the mesopores are distinguished by having the diaphragms more
crowded than they are in the zoccial tubes. A radial arrangement of the cells
about the acanthopores, as shown in fig. 45, is frequently noticeable. Both sets of
acanthopores about equally numerous, but the smaller set is liable to be overlooked
except when the walls are unusually thin.

Mus. Reg." Nos. 6021, 8306.

These species and varieties gave me more trouble than the whole genus Homo-
trypa. It seemed impossible to draw up a thoroughly satisfactory classification of the
hundredsof Minnesota specimens of Dekayella studied. The separations made were
generally recognizable, and some of them are based upon not only obvious, but upon
what, as a rule, we may regard as important structural deviations. Extended inves-
tigation, however, seemed to show that in the present cases the peculiarities were
too inconstant to deserve specific recognition. The var. simplex appears to be the
best marked and most constant, and should, perhaps, have been called a good species,
with var. nevigera under it. In that case the var. echinata also should be raised to
Var. multipora.]

BRYOZOA. 273,

the rank of a species. Variety multipora, however, though often very distinct (com-
pare figs. 43 and 45, plate XXIII), is too intimately connected with the typical form
of the species to admit of greater than varietal distinction.

My reasons for employing the adopted classification instead of the one just
suggested, and which I really believe to be the best, are dominated by the fact that
very similar variations are encountered in large collections of D. ulrichi Nicholson,
Sp., an exceedingly common species at Cincinnati, Ohio. This fact makes it, I think,
not only desirable but necessary that these Minnesota lower Trenton forms be
studied in connection with the various Cincinnati types of the genus. The most
important point to be determined by such a study relates to the origin of the Cin-
cinnati varieties mentioned as being similar to those here separated from prenuntia.
Did the two sets of varieties have a separate origin, or did those above defined con-
tinue and develope into the supposed varieties of D. wlrichi? Although these ques-
tions, whose final solution would require months of careful labor, cannot now be
answered definitely, sufficient data have accumulated incidentally to render it more
than probable that a separate origin for the two sets is more nearly the truth of the
matter. In other words, | believe that future investigation will prove that D. ulricht
was developed from some descendant of D. prenuntia, that the known varities of the
latter became extinct before the close of the Trenton, and that in the Utica and
Hudson river eras a new set of forms was developed from the D. ulrichi stock.*

Comparing D. prenuntia and D. ulrichi it is evident that the two species are
closely related. In the tabulation of the zocecial tubes, which is the least variable
character in both, they are almost identical. The acanthopores furnish the only
reliable point of difference, these structures being much more abundant in D. ulrichi.

Formation and locality —The typical form and var. multipora are common in the middle third of the
Trenton shales at St. Paul, Minneapolis, and localities in Goodhue and Fillmore counties. Var. simplex
occurs in the lower and middle thirds at St. Paul and Minneapolis, while var. nevigera is as yet known
only from Fillmore county, where it was found in the lower third of the shales. The var. echinata is rare
in the upper part of the middle third of the Trenton shales at Minneapolis, but abundant in the lower
part of the upper third at St. Paul, and near Fountain, Minnesota.

 

*Jt may be well to add that the var. echinata will probably prove to be the stock that produced Heterotrypa on the
one side and true Dekayia on the other. Also that the small Dekayella obscura of the Cincinnati rocks may be a degen-

erate descendant of the var. multipora.

—18
274 THE PALEONTOLOGY OF MINNESOTA. ;
[Dekayia.

Genus DEKAYIA Edwards and Haime.

Dekayia, EDWARDS and Hate, 1851, Mon. Pol. Foss. Terr. Pal., p. 277; NicHouson, 1879, Pal.
Tab: Corals, p. 291; 1881, ‘‘Genus Monticulipora,” p. 98; ULRICH,
1882, Jour. Cin. Soc. Nat. Hist. vol. v, p. 155, and vol. vi, p. 148; also
1890, Geol. Sur. Ill., vol. viii, pp. 371 and 415. .

Zoaria irregularly ramose; branches subcylindrical or compressed, growing
from a broad base. Zocecia polygonal, walls thin. Mesopores wanting or very few,
when present restricted to the macule. Acanthopores originating in the outer part
of the axial region, in most cases rather widely separated, often of large size; In
other cases small, and in one instance equalling the zocecia in number. Diaphragms
straight, in most cases remote, sometimes from one-half to one tube diameter dis-
tant in the peripheral region; wanting usually in the axial region. A thin calca-
reous pellicle often drawn over the zocecial apertures.

Type: D. aspera Ed. and H., Hudson River group.

For remarks see under Dekayella, p. 269. For more detailed observations and
full descriptions of all the known Lower Silurian species, the reader is referred to
my “American Paleozoic Bryozoa.”* Beside the following, another as yet unde-
scribed species of Dekayia, with fewer diaphragms, thinner walls and smaller acan-
thopores than D. trentonensis, occurs in Minnesota. It is rather rare, and so far
known only from the Galena shales of Goodhue county.

Dexayia TRENTONENSIS Ulrich.
(Not Figured.)

Dekayia trentonensis ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. vi, p. 151. ,

Zoarium dendroid, branches compressed, dividing frequently and rather irregu-
larly, 4to 10 mm. in width. Entire hight of zoarium probably not exceeding 8 or 9
em. Surface even, or with low rounded monticules, 2.5 mm. apart; the latter occu-
pied by clusters of cells a little larger than those in the intermediate spaces, and
occasionally have a few mesopores at their summits. Zoccia with comparatively
thick walls, their apertures subangular, about fourteen.in 3 mm. Acanthopores
rather large, moderately prominent at the surface where six or seven are to be
counted in 3 mm.

Internal characters: Jn the axial region of vertical sections the tubes have very
thin and slightly flexuous walls, and are crossed by diaphragms from two to four
times their diameter distant from each other. Bending into the peripheral region

 

*Jour. Cin. Soc. Nat. Hist., vol. vi, pp. 84 and 148-155.
Calloporide.] BRYOZOA. 27 5

with a gentle curve, the walls become thickened and the diaphragms more abund-
ant, the7intervals between the latter varying here from one-fourth to one tube-
diameter, with seven in 1 mm. measuring from the surface of a fully developed
example. Acanthopores originating in the outer part of the axial region, large and
readily distinguished. — Tangential sections with the walls rather thick and consist-
ing of a central space, generally of light color, representing the original walls, and
a dark ring-like deposit immediately about the zoccial cavities. On the whole the
structure and thickness of the walls ‘is much as in Dekayella prenuntia, var. simplex
(pl. XXIII, figs. 41 and 42). The acanthopores are isolated, occupying the points of
junction between every three, four or five zocecia. Their large size makes them very
conspicuous in sections passing through deeper levels in which the walls are thinner
than described.

In this species the diagnostic characters of Dekayia are not yet fully developed,
the diaphragms being too numerous. A revision of the Heterotrypide would prob-
ably remove it to Dekayella. A more typical, but undescribed species, with fewer
diaphragms “and smaller acanthopores, is sometimes associated with D. trentonensis
in the Galena shales. Dekayella echinata, which at first I confounded with the
present species, has more numerous diaphragms, thinner walls, and a small set of

acanthopores.

Formation and locality.—Rather rare in the upper third of the Trenton shales and in the overlying
Galena shales at St. Paul, and near Cannon Falls, Minnesota. The original types are from the shaly por-
tion of the Trenton at Burgin, Kentucky. The species is to be found also at Frankfort and other localities

_ in that state, associated with Prasopora simulatria Ulrich.

Family CALLOPORIDA, Ulrich.
Genus CALLOPORA, Hall.

Callopora, HALL, 1852, Pal. N. Y., vol. ii, p. 144, and 1887, Pal. N. Y., vol. vi, p. xv; NICHOLSON, 1874,
Pal. Ontario, p. 61, and Geol. Mag., n. s., vol. i, p. 13; ULRICH, 1882,
Jour. Cin. Soc. Nat. Hist., vol. v, pp. 154 and 251; also 1890, Geol. Sur.
Tll., vol. viii, pp. 372 and 416; ForRsTs, 1887, Bull. Sci. Lab. Denn.
Univ., vol. ii, p. 172.

?Callopora, DYBOWSEI, 1877. Die Chetetiden, p. 106.

Zoarium usually ramose, rarely subfrondescent, or pyriform; surface smooth or
tuberculated. Zocecial tubes with thin walls, varying according to the number of
mesopores from circular or oval to polygonal in cross-section. Apertures closed in
the perfect state by centrally perforated and often radially marked or ornamented
plates, which are left behind as growth proceeds to form floors (diaphragms) of
Mesopores angular or rounded, more or less numerous, some-

succeeding layers.

times surrounding the zoccia; closely tabulate. Zocecial tubes attaining their full
276 THE PALEONTOLOGY OF MINNESOTA.
[Callopora.

development slowly, with closely arranged diaphragms in the attenuate proximal
ends, and fewer or no diaphragms in the middle part of their length. In the per-
ipheral region these structures commonly increase again in number. Transverse
sections show that in the axial region the tubes are of two sizes, the larger ones
with six, seven, and most commonly eight sides, the smaller set four- or five-sided.

Type: C. elegantula Hall. -

Thin sections of Callopora, vertical and transverse especially, exhibit a striking
uniformity of structure, so that it is often difficult to discriminate between those of
closely allied forms. Slight though generally recognizable peculiarities in the tab-
ulation of the zocecial tubes characterize the various species, but in a general way
the distribution of the diaphragms is essentially the same in all. The axial or prox-
imal end of the tubes always has diaphragms--sometimes only one or two (see
plate XXII, fig. 15)—while these structures may be wanting in the rest of the tube,
excepting one or two in the peripheral region. In other cases they will occur
throughout, but in every instance they ‘are less crowded in the central part of the
tube than in its inner and outer parts (see plate XXII, fig. 36). ~

The twenty-five distinguishable forms now known to me of this, one of the best
characterized and most easily recognized genera of the Trepostomata, are distributed
through the various horizons intervening between the Birdseye and the top of the
Upper Silurian, one or more species being characteristic of every recognized geo-
logical division embraced in the interval. Nearly all the species again are to be
numbered among the common fossils, so that they may be said to be of the first
importance to the stratigrapher. The described species are distributed as follows:
In the Birdseye shales of Minnesota, C. angularis, C. incontroversa. and C. undulata;
in the overlying Trenton and Galena shales, C. dumalis, C. ampla, C. multitabulata,
C. goodhuensis, C. crenulata, C. persimilis, and C. pulchella; in the four horizons of the
Cincinnati group going upward (1) C. nodulosa (Nicholson), C. sigillaroidea (Nich.),
(2) C. subplana Ulrich, C. dalei (Edwards and Haime), C. andrewsi (Nich.), C. ramosa
(@Orb), (8) C. subnodosa Ulrich, (4) C. n. sp.; in the Clinton, C. magnopora Foerste;
in the Niagara, C. elegantula Hall; and in the Lower Helderberg, C. perelegans
Hall.

The affinities of Callopora doubtlessly are with the Diplotrypide and, but for the
perforated closures of the zocecia in Callopora, * would recommend placing the genus
in that family. Aside from the closures, which, though they may really have existed,
have not been noticed in any member of that family, and a difference in the method
of growth, the zoaria of the one being ramose, of the other massive, Callopora and
Diplotrypa (in the restricted sense recently employed by me*) are very similar. It

*Contri. to’the Micro.-Pal. of the Cambro-Sil. Rocks of Uanada, pt. ii, p. 32,1889,
BRYOZOA. 277

Callopora angularis.]

8 true the zocecial tubes of the latter are larger than is ustial in Callopora, yet even
in this respect the genera are brought together by C. magnopora Foerste, of the Clin-
ton rocks of Ohio. In the remaining features the agreement is marked, both having
more or less numerous mesopores and no acanthopores, while the tabulation of the
tubes is essentially the same in the two genera, the proximal ends of the tubes being
crossed by numerous diaphragms.

Batostoma, another genus of that family, also agrees closely with Callopora, the
principal differences being the abundant presence of acanthopores, an irregularity
in the tabulation and walls of the axial portion of the tubes, and the more ring-like
character of the peripheral part of the zocecial investment in Batostoma. These
differences, however, are less obvious when we compare some of the earlier species
referred to the two genera. Take, for instance, B. decipiens and B. winchelli, and C.
angularis, of the Birdseye shales of Minnesota. In these species the mesopores are
very few, the tabulation of the tubes alike in essential respects, and the axial region
in transverse sections made up of large and small tubes. As differences we note that
the Batostome have the walls more irregular in the axial region and thicker in the
peripheral, and possess acanthopores, which are wanting in the Callopora.

Simple forms of the genus like C. angularis and C. multitabulata also remind one,
especially in tangential sections, of Monotrypella, but it is more than doubtful that
this resemblance indicates relationship. In any event I am now satisfied that I was
in error in placing C. multitabulata with Monotrypella. This species differs from ordin-
ary Callopore only in having fewer mesopores and more diaphragms, both points of
slight importance. True Monotrypella is distinguished at once from Callopora by the
subequal size of the tubes in the axial region of transverse sections. .

7

CALLOPORA ANGULARIS, %. sp.

PLATE XXII, FIGS. 37-41.

Zoarium small or of medium size; branches 3 to 5 mm. in diameter. Zocecial
apertures angular, subequal, about nine and a half in3mm. Mesopores very few,
occurring chiefly in small clusters. Walls rather thin, ridge-shaped.

Internal characters: Vertical sections show numerous diaphragms, whose distri-
bution in the outer third of the section is shown in fig. 38 better than can be
described. In the central third the proximal ends of the tubes increase very slowly
in size. Here the diaphragms are also closer together than higher up in the tube.
The axial region therefore appears as made up of two sets of tubes, one large with
diaphragms averaging 0.25 mm. apart, the other small with diaphragms from 0.1 to
278 THE PALEONTOLOGY OF MINNESOTA.

{Callopora incontroversa.

0.2 mm. apart. In tangential sections of fully matured examples (fig. 39) the zocecia
are decidedly angular, subequal, most of them in contact on all sides, the mesopores
being small, very few, and sometimes restricted to certain spots where limited
clusters may be found.

Both the mesopores and diaphragms are less numerous than in C. multitabulata;
the angular shape of the zoccial aperture will distinguish the species from other
forms of the genus. I found it difficult to separate slightly abraded specimens of a
small form of Batostoma, near B. winchelli, from those of the present species. When
unworn the Batostoma has distinct acanthopores which are a sufficient mark, and
when these have been removed by abrasion the student may succeed in separating
them by measurement, the latter having eleven or twelve zocecia where C. angularis

has nine or ten.

Formation and locality.—Rather rare in the lower third of the Trenton shales at Minneapolis,
Chatfield, and near Fountain, Minnesota.

Mus. Reg. Nos. 8088, 8097.

CALLOPORA INcCONTROVERSA Ulrich.
PLATE XXII, FIGS. 33-36.

Callopora incontroversa ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 96.

Zoarium ramose ; branches smooth, subcylindrical, 4.5 to 6 or 7 mm. in diameter,
dividing dichotomously at intervals of 12 or more mm. Zocecia with walls compar-
atively thin ; apertures oval or subcircular, rarely polygonal ; small, inconspicuous,
and rather irregularly distributed clusters consisting of openings slightly larger than
the average occasionally present; about ten apertures in 8 mm. Closures occa-
sionally preserved; central perforation larger than usual, 0.07 to 0.08 mm. in
diameter, enclosed by a thickened rim; apparently not radially marked, Mesopores
numerous, small, scarcely gathered into clusters, usually occupying only the spaces
left between the contiguous rounded walls of the zocecia.

Internal characters: Tangential sections show that the zoccia are broadly
elliptical, rather thin-walled, and usually in contact with each other at as many
points as their rounded form will admit. Interspaces occupied by the mesopores.
At unequal intervals the latter may be more numerous and the zoccia a little
larger than usual, but these clusters are never conspicuous. In vertical sections the
tubes form a gradual but rather short curve to the surface. In their tabulation and
general appearance the proximal ends of the zocecial tubes are so much like the true
mesopores of the peripheral region that we cannot escape the conviction that their
functions alzo were alike. From the point of origin till it has attained nearly its
BRYOZOA. 279

Callopora undulata.)

mature size, the tube is crossed by from ten to twenty or more closely and regularly
arranged diaphragms. After this the diaphragms are much farther apart, and in
many tubes may be wanting entirely until they enter the peripheral region when
they once more come close together.

This species is distinguished from C. undulata by its slightly larger size, smooth
surface, and slight differences in the tabulation®of the tubes. In tangential sections
the zocecia of that species are less rounded. C. goodhuensis and C. ampla have fewer
mesopores and more abundant diaphragms.

Formation and locality—Rather rare in the lower third of the Trenton shales at Minneapolis,
St. Paul and Preston, Minnesota.

Mus. Reg. No. 7653.

CaLLopora unDuLATA Ulrich.
PLATE XXII, FIGS. 24-31.

Callopora undulata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur, Minn., p. 95.

Zoarium ramose, branches slender, averaging about 2.5 or 3.0 mm. in diameter,
dividing dichotomously at intervals of 10 mm. or more. Surface with rather large,
rounded monticules, that usually coalesce laterally, forming transverse ridges, or
more or less complete annulations, five in ten mm. In some fragments and portions
of others the monticules are separate, while in a few they are nearly obsolete. Zocecia
with moderately thin walls, subangular or ovate apertures, of nearly equal size over
all portions of the surface ; ten or eleven in 3mm. Mesopores comparatively few,

‘guia, not readily distinguished externally, their mouths usually closed. Zoccial
covers not observed.

Internal characters: These are sufficiently shown in the illustrations, and, as
they are also very similar to those of the preceding species, I shall only point out
the differences. The walls in tangential sections are thicker than in C. incontroversa,
the divisional line between adjoining zowcia more distinct, and the mesopores less
numerous.

C. angularis has a smooth surface, fewer mesopores, and more crowded dia-
phragms. C. ampla is distinguished in like manner, and C. incontroversa, externally,
by its smooth surface and more rounded zocecial apertures.

Formation and locality.x—Not uncommon in the upper part of the middle third of the Trenton shales

at Minneapolis and St. Paul, Minnesota.
Mus. Reg. No. 8113.
280 THE PALEONTOLOGY OF MINNESOTA.

[Callopora multitabulata.

CaLLOPORA MULTITABULATA Ulrich.
PLATE XXIII, FIGS. 11, 12, 16, 17, 24, 25, 26, 30, 31.

Monotrypella multitabulata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 100.

Zoarium consisting of more or less irregularly divided, subcylindrical branches,
their diameter averaging 7 or 8 but warying between the extremes of 3 and 10 mm.
Surface generally with more or less strongly elevated, conical or rounded monticules,
2.5 mm. from center to center. The typical form of the species occurs in the Trenton
of Kentucxy and Tennessee, and in the upper third of the Trenton shales of Minne-
sota. In this monticules are always present, and they are occupied by zoccia but
little if at all larger than the average. Mesopores are exceedingly few at the
surface, the zocecia being angular, in contact with each other, their walls thin ;
apertures direct, with an average of eleven in 3mm. Closures preserved in a few
specimens, ornamented as shown in fig. 26. In the underlying middle third of the
shales and in the overlying Galena shales there is a form, rare in the first, exceed-
ingly common in the second, that varies in having the monticules lower and even
quite inconspicuous, the zocecia a little larger (ten in 3mm), and the cells occupying
the low monticules usually well distinguished by their size. Very frequently too a
sprinkling of mesopores is detectable at the surtace, as shown in fig. 31, but it is rare
to find them as numerous as in fig. 30.

Internal characters: In tangential sections of the typical form the zocecia are
regularly polygonal, generally in contact with each other on all sides, and provided
with moderately thickened walls, in which the original boundary line between the
zocecia is preserved as a sharp dark line. Mesopores are very few. Because of a
lack of room no section of this form was illustrated, but a good idea of its appear-
ance may be gathered from fig, 39 on plate XXII, and the upper third of fig. 17 on
plate XXIII. In the Galena shales variety the appearance of tangential sections is
generally as in the mentioned fig. 17.

In vertical sections (pl. XXIII, fig. 24) the peripheral region is comparatively
wider than in other species of this type. Diaphragms exceedingly abundant
throughout the tubes, the average distance between them in the axial region being
about equal to their diameter; in the peripheral region twelve to sixteen occur in 1
mm. Here many of them may be slightly curved or joined to one another. An
occasional mesopore is met with in these sections. These are very closely tabulated,
the average number in 0.5 mm. being ten. Now and then one of the mesopores
may widen and assume the characters of a true zocecium.

In the central part of transverse sections the size of the tubes and the appear-
ance in general is intermediate between figs, 20 and 21 of plate XXIII.

\
BRYOZOA. 281

Callopora ampla.] *

The diaphragms are more numerous in this species than in any other known to
me. Very closely allied, however, are C. angularis, C. ampla and C. goodhuensis. The
first is distinguished by its smaller size, smooth branches and somewhat less crowded
diaphragms, especially in the mesopores; the second by its smooth branches, nar-
rower peripheral region, slightly larger zocecia and more numerous mesopores; the
third is smaller, with smaller zocecia and more abundant mesopores.

Formation and locality.—In Minnesota the species is rare in the middle third of the Trenton shales
at Minneapolis, rather abundant in the upper third at St. Paul and in the vicinity of Cannon Falls, and
exceedingly abundant in the Galena shales at many localities in Ramsey, Goodhue and Fillmore counties.
Also a common fossil of the Trenton at several localities in central Kentucky, and near Nashville, Ten-
nessee. The same species apparently occurs at Ottawa, Canada.

Mus, Reg. Nos. 3485, 7652.

CALLOPORA AMPLA, ”. Sp.

PLATE XXIII, FIGS. 15, 18-20, 22, 23, 27, 28.

This form is very closely related to C. multitabulata, and doubtlessly belongs to
the same line of development. Under the circumstances it will be sufficient to
point out its peculiarities. The growth is less compact, the branches, though fully as
large as in that species, being, as a rule, less frequently divided. Except in rare cases
the surface is without monticules, and while there are clusters of zocecia appreciably
larger than the average they are never conspicuous except when elevated into mon-
ticules. The zocecia are larger, with an average of nine in 3 mm., the apertures a
little oblique, drawn out lengthwise and apparently more shallow, while the occa-
sionally preserved closures seem to be without ornamentation. The form of the
apertures may be oval or angular, the first when mesopores are comparatively
abundant, the second when they are few and very small. In both cases, however,
thin sections are generally required to demonstrate the existence of the latter. In
most instances the mesopores are fewer than in fig. 18, and as a rule they occupy the
angles of junction between the zocecia where, when the surfacé is a little weathered,
they often appear as acanthopore-like elevations.

Comparing internal characters we find that in C. ampla the tubes in the axial
region are generally of larger size, and that they curve to the surface more slowly.
The fully developed peripheral region is much narrower than in specimens of the
same size of C. multitabulata (compare figs. 19 and 22 with 24 of plate XXIII), the
superficial crowding of the diaphragms more sudden, and the intervals between
them throughout the axial region a little greater. The last difference, however,
does not apply when we compare the Galena shales varieties of the two species.
These often agree so closely in every other respect as well that a rigid distinction
282 THE PALEONTOLOGY OF MINNESOTA.

[Callopora goodhuensis.

between them is almost if not quite impossible. How else can we. explain this fact.
than by assuming that the two forms gradually and by almost equal concessions
approximated in structure ?

Compared with other species C. angularis will be found to be smaller, with
smaller and more equal-sided zocecia and fewer mesopores. C. goodhuensis is smaller

in every respect.

Formation and locality.—Rather abundant in the upper layers of the middle and in the lower part
of the upper third of the Trenton shales at various localities in Ramsey, Goodhue and Fillmore counties,
Minnesota. Common also at many localities in the state where the Galena shales are exposed, and in
equivalent beds at Decorah, Iowa.

Mus. Reg. Nos. 7640, 7659, 8067.

CALLOPORA GOODHUENSIS, 7. Sp.

PLATE. XXIII, FIGS. 9, 10, 21, 29.

This also is closely related to C. multitabulata. As a rule the surface is without
monticules, and they are never prominent, while the average size of the branches is
less, the average diameter being between 4 and 5 mm. The zoccia are smaller,
especially at the center of transverse sections, their apertures subangular, rather
oblique in young examples, nearly direct in those full-grown, with twelve or thirteen
in38mm. Internal characters very similar, excepting that the peripheral region is
comparatively narrower, being in this respect more like C. ampla.

Mesopores more numerous and more closely tabulated than in C. angularis.
The zocecial apertures, on the other hand, are more direct in that earlier species.

Formation and locality—Common in the Galena shales at St. Pauland near Cannon Falls, Minnesota.
Mus. Reg. No. 8111.

CALLOPORA DUMALIS, 1. sp.

PLATE XXIII, FIGS. 1-8.

Zoarium bushy, attaining a width of 50 mm. or more, consisting of numerous
small inosculating branches, varying between 1 and 2.5 mm. in diameter, but with
1.5 mm. by far the most common size. In young stages the zocecial apertures are
more or less oblique and ovate, the mesopores rather numerous and some of them of
large size. In old fragments the latter are fewer and of small size, and the zocecial
apertures more direct and polygonal. Closures with faint radiating lines: central
perforation rather small. Measuring diagonally about six zocecia in 1.5 mm.

Internal characters as shown in figs. 7 and 8. Vertical sections show that while
diaphragms are rather abundant in all parts they are not excessively crowded in the
peripheral region. In this respect the species differs from the species grouped about
C. multitabulata.
BRYOZOA. 283
Callopora pulchella.]

The small size of the branches and bushy habit of growth distinguish the species
from all the other known Minnesota species of the genus. Externally its zoaria are
exceedingly like those of an undescribed form occurring in the Cincinnati quarries
associated with C. dalei Ed. and H.

Formation and locality.—Very abundant in the upper third of the Trenton shales, rare in the Galena
shales, at St. Paul and Cannon Falls, Minnesota.

Mus. Reg. No. 8112.

CALLOPORA PULCHELLA, ”. Sp.

»

PLATE XXII, FIGS. 1-12,

Zoarium dendroid, branches averaging 5 mm. in diameter, tapering slightly, the
oldest parts sometimes attaining a diameter of 7 mm., the young extremities only 3
or 4mm. The branches divide dichotomously at average intervals of 12 mm., and
never, so far as observed, inosculate. Surface exhibiting small conical monticules,
2.0 to 2.5 mm. apart, their summits generally with small aggregations of mesopores.
As shown in the figures, the hight of the monticules varies in different examples, and
in some they are to be described as rounded rather than conical. Zocecial apertures
small, subcircular, enclosed by rather thick, ridge-shaped walls, regularly arranged,
subequal, thirteen or fourteen in 8mm. Mesopores very small and, though numer-
ous, often difficult to distinguish externally with an ordinary pocket lens. This
difficulty is greatest in old examples in which they are partially filled by calcareous
deposits.

Internal characters: Vertical sections show that in the axial region the prox-
imal end of the tubes is crossed by from two to four diaphragms, beyond which these
structures are absent till we reach the middle of the comparatively wide peripheral
region when each zocecial tube is again intersected by one or two. Mesopores are
abundant and closely tabulated. In tangential sections the zocecia are subcircular,
their walls somewhat ring-like and in contact with each other in only a limited
degree, the interspaces being occupied by more or less numerous mesopores varying
considerably in size and shape. Just beneath the surface of a fully matured example
the walls are thickened by internal deposit, the mesopores small and approximately
of uniform size. At deeper levels the walls are thinner and the mesopores larger and
more irregular in shape and size. In transverse sections the axial region is made
up of decidedly angular tubes of which those of the larger set are also comparatively
small, while those of the minor set are less regularly distributed than usual.

This form is to be compared with the C. dalet Edwards and Haime, of the Cin-
cinnati group, from which it differs chiefly in having fewer diaphragms and slightly
‘

284 THE PALEONTOLOGY OF MINNESOTA.

(Callopora pulchella var. presimilis.

smaller zocecia. Excepting the following variety there is no Minnesota species of
Callopora known that is likely to be confounded with C. pulchella, but care is required
in separating it from the associated Homotrypa tuberculata,

Formation and locality—Common in the upper third of the Trenton shales at St. Paul and near
Cannon Falls, Minnesota.

Mus. Reg. Nos. 8033, 8114.

CALLOPORA PULCHELLA, UV@7’, PERSIMILIS, ”. Var.

‘

PLATE XXII, FIGS. 13-17.

This variety differs from the typical form of the species in having more prom-
inent tubercles, thinner zocecial wills (causing the apertures to be correspondingly
larger), more readily distinguished and, as a rule, more numerous mesopores, even
fewer diaphragms, and in the greater size of the tubes in the axial region. The
growth of. the zoarium and the number.of zoccial apertures in 3 mm. (thirteen or
fourteen) is the same. Indeed, the points of difference even are not constant. We
cannot, therefore, doubt the propriety of referring the form to C. pulchella. On the
other hand it is impossible to distinguish var. persimilis, by external comparison of
fragmentary material alone, from the later C. ramosa d’Orbigny, one of the most
common Bryozoa of the Cincinnati rocks. It is true the zoaria of the Trenton form
never grew to such a size nor do the branches inosculate as in the Cincinnati species,
but such differences the student will find of little practical use when, as usual, frag-
ments are to be identified. Luckily, the interior furnishes us with a guide in the
relative number of diaphragms, these being much more abundantly developed in the
Cincinnati species than in the Trenton variety. For further remarks relating to
this subject see ante. p. 215.

Formation and locality.—Associated with Phylloporina corticosa, Trigonodictya conciliatrix and
Prasopora conoidea, all characteristic species ot the upper third of the Trenton shales, at Poe’s farm,
near Cannon Falls, Minnesota.

Mus. Reg. No. 8115.

CALLOPORA CRENULATA, ”. Sp.

PLATE XXII, FIGS, 18-23,

Zoaria forming rather large, compactly interwoven, bushy masses, consisting of
strong branches that divide and inosculate most irregularly and frequently; average
thickness of branches 7 or 8 mm., but some may be over 10 mm., and as many only
4 or 5 mm. Surface generally with rounded monticules, occupied by clusters of
zocecia larger than the average, and by greater or less aggregations of small meso-
Diplotrypa.] BRYOZOA. 985

.

pores. Zocecial apertures rounded, mostly subcircular, regular, twel¥e or thirteen
in 3mm. Closures preserved in one out of about forty specimens, slightly concave,
apparently smooth and without a raised rim about the central perforation. Walls
of moderate thickness, ridge-shaped. Mesopores numerous, rather small, but dis-
tinctly visible under a good pocket lens.

Internal characters: These are remarkable chiefly in vertical sections, tangential
and transverse sections being very much like those of C. pulchella and C. ramosa.
In vertical sections namely there seems to be a total absence of diaphragms, not
only in the zoecial tubes but in the mesopores as well. Another peculiarity is the
crenulated or wavy character of the walls in the axial region that has suggested
the specific name. This crenulation is shown very distinctly when the tubes are
exposed by vertical fractures.

The two peculiarities mentioned in the preceding paragraph distinguish the
species from all the others now referred to the genus. In other respects we are
reminded of its associate C. pulchella, yet they ought in no case to be confounded,
since in that species the branches are more slender and do not inosculate, and the
zoccial apertures are appreciably smaller.

Formation and locality—Not uncommon in the upper third of the Trenton shales at St. Paul and
near Cannon Falls, Minnesota. Rare in the Galena shales (here almost invariably without monticules)
at the same localities, and at Decorah, Iowa, and Neenah, Wisconsin.

Mus. Reg. Nos. 8019, 8038, 8068, 8082.

é

Family DIPLOTRYPIDA, Ulrich.

For remarks on this family see pp. 276 and 290.

Genus DIPLOTRYPA, Nicholson.

Zoaria massive or discoid, generally free. Zocecial tubes comparatively large,
with thin prismatic walls, and horizontal diaphragms. Mesopores few to numerous,
varying in size, many of them enlarging gradually and assuming the characters of
true zoecia. Acanthopores wanting.

Type: D. petropolitana Pander, sp.

The relations of this genus are with Batostoma on the one hand and Monotrypa
and Callopora on the other. Species are few and, so far as known, all belong to Lower
Silurian rocks, The two about to be described are aberrant in having very few

mesopores.
286 THE PALEONTOLOGY OF MINNESOTA.
- {Diplotrypa limitaris.

DIPLOTRYPA LIMITARIS, ”. Sp.

 

 

Fig. 18. Diplotrypa limitaris Ulrich, upper beds of the Galena shales, Goodhue county, Minnesota.
Collection of E. O. Ulrich. Transverse and vertical sections, x 18, showing the tabulation of the tubes
and the great reduction in the number of mesopores characterizing the species.

Zoarium, as seen in four specimens, small, hemispherical], 12 mm. or less in diam-
eter, and 8 to7 mm. in hight. Under surface concentrically wrinkled ; upper surface
without monticules but presenting rather conspicuous clusters of large cells among
which the mesopores are commonly more numerous than elsewhere. Walls very
thin ; zocecial apertures polygonal, 0.25 to 0.4 mm. in diameter, with ten to twelve
in3mm. Mesopores of variable size, not as numerous as the zowecia. Tabulation
of tubes comparatively regular and uniform; in the mesopores there are nine or ten
diphragms in 0.5 mm., in the zocecial tubes six to nine in 1 mm. As shown at the
margin of the vertical section figured above, the tabulation of the mesopores changes
suddenly (? always) into that of the zocecia. :

The unusually small number of mesopores distinguishes this species from D.
petropolitana and D. westoni (Ulrich). In those species the zocecia are also some-
what larger, and the tabulation less uniform. .

Compared with associated and other discoidal Bryozoa, the species of Mesotrypa
are separated by their rounded zocecia and much more abundant mesopores, those
of Prasopora by the cystiphragms, those of Leptotrypa by their acanthopores, while
those of Monotrypa are entirely without mesopores.

Formation and locality.—Upper beds of the Galena shales at localities in Goodhue county, Min-
nesota. The best exposure of these beds is in a bluff about thirteen miles south of Cannon Falls.
Diplotrypa neglecta.] BRYOZOA. 987

DIPLOTRYPA NEGLECTA, 7”. SD.

 

Fa. 19. Diplotrypa neglecta Ulrich, base of Galena limestone, Hader, Goodhue county, Minnesota.
Collection of E. O. Ulrich. 1and 2, two tangential sections, x 18, and 3, a vertical section, similarly
enlarged.

Zoarium a small subconical or hemispheric mass, about 12 mm. in diameter and
8 mm. in hight. Tube walls thin, transversely rugose, appearing quite irregular
and rough in longitudinal fractures. Zocecia about nine in 3 mm., not regularly
arranged, polygonal, largely in contact with each other, the mesopores being few in
number and variable in size and distribution. Clusters of large zocecia occur and
among these the mesopores may be more abundant than in the intermediate
spaces.

In transverse sections we see cells of all sizes up to 0.45 mm., and not infre-
quently it is difficult to discriminate between the smaller zocecia and the mesopores.
As is shown by vertical sections the two sets of tubes are not totally distinct,
the mesopores being in many cases clearly superseded by zoccia. Perhaps on
account of the rugosities of the walls the mesopores often appear as developed
periodically. The diaphragms are irregularly distributed, from one-half to four
times their diameter distant in the large tubes and averaging about 0.15 mm. apart
in the mesopores.

Though possessing all the essential characters of the genus, the internal irregu-
larly and other peculiarities of the species are so obvious that comparisons are

unnecessary.

Formation and locality Lower part of the Galena limestone, at Hader, Goodhue county, Min-
It is here associated with Mesotrypa (?) rotunda Ulrich, Plectambonites gibbosus W .and S.,

nesota.
Ulrich, Fusispira ventricosa Hall, and other fossils described in this volume.

Pleurocystites angulatus
288 THE PALEONTOLOGY OF MINNESOTA.

[Batostoma.

Genus BATOSTOMA, Ulrich.

Batostoma ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 154; 1890, Geol. Sur. Ill., vol. viii, pp.
379, 459; FoorD, 1883, Contri. Micro-Pal. Cam.-Sil. rocks Can., p. 17.

Zoaria irregularly ramose, with a large basal expansion. Zocecial walls thin,
and irregularly flexuous in the axial region, more or less thickened in the peripheral.
In the most typical species the walls are irregularly ovate, thick and ring-like in
tangential sections, with neighboring zocecia in contact only at limited points, the
mesopores numerous, closed at the surface, and irregular in shape and size, and the
acanthopores abundant and with a larger central cavity than usual. Species vary
from these to forms having polygonal, thin-walled zocecia and very few mesopores
and acanthopores. Diaphragms strong, horizontal, complete, few or wanting in the
axial, more or less abundant in the peripheral region. In the axial region of trans-

' verse sections the tubes are divisible into two sets, one larger than the other.

Type: B. implicatum Nicholson, sp.

Beginning in the Birdseye limestone and shales of Minnesota with B. fertile,
B. magnopora, and an undescribed species, it is evident that, the same as with
Callopora and Dekayella, the primitive stock of the genus was of the simplest type.
Mesopores were few, the zocecia angular and thin-walled, and acanthopores both
few and very small. And yet the first of these species varies by most gentle degrees
to forms (B. fertile var. circulare) having numerous mesopores, circular zocecial aper-
tures, and thick walls—in short to a form that approximates the most typical and
fully developed species of the genus. .

In B. implicata and B. jamesi Nich. sp., of the lower half of the Cincinnati group,
the zocecia are characterized by thick ring-like walls, irregularly oval apertures,
numerous mesopores and acanthopores. Although closely allied, B. variabile differs
conspicuously from them in having few mesopores and polygonal zoccia. Being a

' later species, and one that doubtlessly is a direct descendant of those forms, we are
justified in assuming that a reversion in structure toward the primitive type took
place during the closing times of the Lower Silurian. While such a tendency seems
to have been general it was by no means universal, since at certain localities (Stony
Mountain, Manitoba, Iron Ridge and Delafield, Wisconsin) where the conditions for
the development of these Bryozoa seems still to have been eminently favorable, the
genus is represented by species with abundant mesopores.

A similar reversion had already taken place during the deposition of the Utica,
in which two of the species, both as yet undescribed, are so simple in their structure
that their really intimate relations to B. jamesi might not be suspected. It is only
Batostoma.] ‘-BRYOZOA. 989.

by making large collections that the affinities of such species can be determined.
When this can be done we find that some specimens exhibit, perhaps over limited
areas only, the full characters of the genus in an indubitable manner.

The mesopores, therefore, are to be considered as the most unstable feature of
| Batostoma. Though they can never be said to be wanting entirely, it is nevertheless
_ true that an inexperienced student might occasionally come to such a conclusion.
Even in the same species great differences in their number may be encountered.
Take B. fertile, for instance, in which such deviations are more strikingly expressed
than in any other species (compare figs. 4 and 7 with 8 and 9 on plate XXV). On
the other hand the peculiar irregularity of the tubes in the axial region seems
always to be present, thus assuring us of a clue to the generic affinities of forms
that, because of the almost total lack of mesopores and practical absence of acan-
thopores may appear to have relations with types differing widely from Batostoma.

Respecting the affinities of the species of Batostoma and the systematic position
of the genus, I have always been in some doubt. At first the Heterotrypide seemed
the most likely family to receive them, but I soon satisfied myself that their rela-
tions did not lie in that direction. Next the Calloporide were suggested, and finally,
as vol. viii of the reports of the Geological Survey of Illinois was going through the
press, I decided to place them with the Diplotrypide, and it is with this family that
I have since arranged them. To-day another arrangement would suit me better.
The fact is that most of my time since the printing of the Illinois work has been
spent on the Bryozoa, and the Jast six months were devoted to the Trepostomata
exclusively. Innumerable comparisons were drawn, many of them resulting in
important genealogical discoveries. But asis intimated on p. 216, the changes in clas-
sification that would be necessary, if the results of my comparative studies were
carried to a logical conclusion, seemed too numerous and great for the present state
of published knowledge. Indeed, I feared that under the prevailing circumstances
it would be difficult to substantiate my claims. It should be remembered that
I work from a basis, or rather with a knowledge of paleozoic bryozoan forms that
exceeds the published lists by several hundred species. Even with the conservative
plan adopted by me, I am obliged continually to draw upon unpublished matter to
prove my points, so that only too often they narrowly escape standing as mere
assertions. Among other changes that I should have liked to make in the scheme
of classification on pp. 105-107, is a reconstruction of the families Calloporide,
Diplotrypide and Trematoporide. In the first place it was a mistake to make
Trematopora the type of the family as defined, because the relationship to Constel-
laria, which more truly expresses the characters of the family intended, is remote
compared with the affinities existing between Tvrematopora and Batostoma. The

-19
290 THE PALEONTOLOGY OF MINNESOTA.

[Batostoma fertile .
latter, I am now fully satisfied, embraces the progenitors of Trematopora, and as the
relationship seems to be very intimate it may be well to consider the advisability
of dropping Batostoma in favor of Hall’s older name. The Calloporide, with Aspi-
dopora removed to the Monticuliporide, might be united with the Diplotrypide, from
which, in that case, it would be well to remove Batostoma.* But for the reasons
stated it was deemed inexpedient to carry out sweeping innovations in the present
work, and the only excuse for their mention here is that it seemed necessary to
publish some idea of the lines in which progressing knowledge is likely to modify
the present classification. Perhaps also to show how well we are acquainted with
its imperfections.

Batostoma FERTILE Ulrich.

PLATE XXV, FIGS. 1-11.

Batostoma fertile ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 92.

Zoarium attaining a large size, 50 to 100 mm. in hight, consisting of strong,
irregularly thickened, more or less compressed branches that divide without regu-
larity; thickness of branches 5 to 25 mm., width 8 to 30 mm. Zocecial apertures
varying according to the size and number of the mesopores and the thickness of the
walls, from polygonal to circular. In some specimens and portions of others meso-
pores are exceedingly few and the zoccial walls thin and generally in contact at all
sides; in the majority of examples mesopores are moderately abundant and the
walls thicker, but the zocecial apertures are still polygonal or at any rate most of
them subangular. From this, the typical form, we can trace the variations by small
degrees into a form which, for the sake of reference, may be designated as var.
circulare. In this the zocecial apertures are almost perfectly circular, enclosed by a
raised rim or peristome, and largely separated from each other by depressed inter-
spaces. Often the peristomes are thicker and more distinctly separated from each
other than is shown in fig. 6. Interspaces occupied by mesopores varying consider-
ably in size and shape. Their mouths are commonly closed by a calcareous plate in
which a variously situated rounded opening may be observed. When the preserva-
tion is unusually favorable the surface of the plate is studded with very minute
papille representing the terminations of exceedingly small foramina. Acanthopores
between one and two to each zocecium, but very small and only in rare instances
distinguishable at the surface.. At intervals of 3 or 4 mm. occur clusters of zocecia
a little larger than the average, and in the center of these usually small substellate
macule. Between eight and nine of the average zocecia in 3 mm.

*The families reconstructed in accordance with the above suggestions would be as follows: CALLOPORIDE, Calopora,
Diplotrypa, Monotrypa, ? Calloporella; TREMATOPORID#, Trematopora, Batostoma,? Hemiphragma, ? Stromatotrypa; CONSTELLAR-
Ip&, Constellaria, Stellipora, Nicholsonella, ? Idiotrypa. $

 
BRYOZOA. 291

Batostoma magnopora.]

Internal characters: In vertical sections the tubes have thin and somewhat
irregularly fluctuating walls in the axial region. Their course to the surface is
gently curved throughout, and as they near the same their walls are appreciably
thickened, while mesopores, whose number varies greatly in different specimens, are
abruptly developed. The mesopores may be constricted at the points where they
are intersected by the diaphragms, The latter are often thickened circumferentially,
and vary somewhat in the number occurring in a given space, seven and eleven in
1 mm. being the extremes so far noticed. In the axial region diaphragms are very
far apart or are wanting entirely, but in the peripheral portion the average distance
between them is about equal to half their diameter. Specimens more than 12 mm.
thick consist of two or more layers of tubes.

The four tangential sections figured on plate XXV, fully illustrate the charac-
ters of the species as brought out in this kind of section. Fig. 7 is from a specimen
with very thin walls, few mesopores, and scarcely distinguishable acanthopores, the
latter being in the angles of junction. Fig. 4 represents a small portion of a section
prepared from the original of fig.2. In this, which is an average example, the walls
are thicker, mesopores more abundant, and the acanthopores, though small, more
readily distinguished. Minute foramina are shown in the diaphragms of some of the
mesopores. Figures 8 and 9 are from specimens of the variety circulare, the first
with thick zocecial walls, the second with them thin as in fig. 6.

: Ina general way this species reminds one more of upper Hudson river species
than of Trenton forms. Variety circulare resembles B. manitobense Ulrich,* very
closely, but the clusters of large zocecia are more conspicuous in that species. The
typical variety on the other hand is more like B. variabile, differing from it chiefly
in the smaller size of the acanthopores. Compared with associated Bryozoa none

save Anolotichia impolita have as large zocecia.

Formation and locality.—Abundant in the lower third of the Trenton shales at Minneapolis and
St. Paul, Minnesota.

Mus. Reg. No. 8136; var. circulare, 8137.

BaTOSTOMA MAGNOPORA, 7%. Sp.

PLATE XXV, FIGS. 12-15.

Zoarium ramose; branches large, subcylindrical, 8 to 15 mm. wide; surface
elevated at irregular intervals into low monticules, the latter broad and occupied
by zowcia a little larger than the average. Zocecia unusually large, about eight in 8
* mm.,, their apertures polygonal, the walls thin, with one or two small acanthopores

 

*Oontr. Micro-Pal. Campbro-Sil. rocks of Canada, pt. II. p. 33, 1889.
292 THE PALEONTOLOGY OF MINNESOTA.

[Batostoma varium.

to each zocecium rising generally from the wall at some point between the angles
of junction. Many of the latter are occupied by small mesopores, but these are to
be regarded as comparatively very few and at all times difficult to distinguish
externally. ,

Internal characters: In tangential sections the tubes are polygonal and have
rather thin walls in which the line of contact between adjoining tubes is distinctly
preserved. Mesopores few, small, chiefly at the angles of junction. Acanthopores
small, inconspicuous. In vertical sections the tubes proceed toward the surface in
avery gentle curve until they enter the unusually narrow peripheral region, where
the curve is sufficiently accelerated to enable them to open at the surface with
nearly direct apertures. Diaphragms are very remote or wanting in the axial
region, and not numerous even in the peripheral portion. Here each tube pre-
sents from one to five, separated by intervals of from one-half to one tube-diameter.
In the mesopores, which appear to be very short, the diaphragms are much closer
with three or four in 0.5mm. In the central part of transverse sections (fig. 14) the
tubes are conspicuously divided into a large and small set, both having very thin
walls,

The large size of the zocecia distinguishes this species not only from all the
other forms of the genus known but from all the associated bryozoans as well.
Anolotichia impolita, restricted to the bed of shales immediately beneath (“Stictopo-
rella beds”), has zocecia fully equalling those of the present species in size, but they
are each provided with a lunarium and are commonly of either rhomboidal or hexa-
gonal shape, while the surface is without monticules and the growth of the zoarium
decidedly irregular. ,

Formation and locality.—Four specimens were found in the middle third of the Trenton shales,
three at Minneapolis, the fourth at West St. Paul. -

BaTOSTOMA VARIUM, 2. Sp.

PLATE XXV, FIGS. 16-25.

Zoarium growing from a large basal attachment into erect branches. These
vary in width from 7 to 20 mm. but average from 10 to 15 mm., are generally a little
compressed and divide most irregularly. In some cases the basal expansion consists
of several distinct layers, varying from 1 to 3 mm. in thickness. Surface without
monticules, but exhibiting instead clusters of orifices larger than the average and
separated by interspaces wider than usual. Not infrequently the center of these
clusters is marked by a small substellate solid macula. Superficial characters
variable, the walls in some cases being thin, with the zoccial apertures subangular,
BRYOZOA. 293

Batostoma montuosum.]

the zocecial walls seemingly in contact in most cases, the mesopores few, and the
acanthopores indistinct. This condition, which is to be counted as rare, corresponds
to fig. 18. From it the usual deviation consists in the rounding and constriction of
the zocecial apertures, and widening of the interspaces. When carried to the extreme
we have subcircular apertures enclosed by a thin peristome, separated by depressed
interspaces in which the mouths of a few mesopores may be noticed. In all these
conditions (corresponding to figs. 16, 19, 20 and 21) the average number of zoccial
apertures in 3 mm. is nine or ten. The acanthopores also are rarely very conspicu-
ous for size, though they are numerous enough and may be distinctly visible on well
preserved examples. But in a variety, or rather an occasionally observed condition
of the species, the acanthopores are much larger and situated three or four in the
now thin walls of each zocecium, causing their apertures to be more or less
indented at the points occupied by them.

Internal characters: The extreme variability of tangential sections is well shown
in the seven figures on plate XXV. And yet the species is an easy one to identify by
means of thin sections. Each tangential section will show from two to four of the
conditions illustrated, and although I used five specimens and six sections I might
have obtained an equal range of variation with two of them. The greater part of
them vary between the appearances represented in figs. 16, 19 and 21. Vertical
sections are more constant, having numerous diaphragms—about four in the zocecial
tubes and six in the mesopores in 0.5 mm.—in the peripheral region, and none in
the axial. The usual irregularity of the tubes in the axial region is noticeable,
Also a peculiar moniliform structure of the walls in the peripheral region is the
probable cause of some of the variations noticed in tangential sections.

The zoarial growth is less robust and the average size of the zocecia less than
in B. fertile, The opposite is the case when compared with B. winchelli, which, like
B. minnesotensis, has also much fewer mesopores. The species is evidently a fore-
runner of B. humile of the Galena shales and B. jamesi Nich. sp. of the Cincinnati

rocks.

Formation and locality.—Moderately abundant in the middle third of the Trenton shales at Min-
neapolis and St. Paul, Minnesota.

Mus. Reg. No. 8135.

BaTosTOMA MONTUOSUM, 7”. Sp.

PLATE XXV, FIGS. 26-28,

Zoarium ramose, small, branches dividing rapidly, 5 to 10 mm. in diameter;

surface with more or less conspicuous monticules, 2.0 or 2.5 mm. apart, occupied by

apertures of the same size as those in the depressions; the summit of the monticules
294 THE PALEONTOLOGY OF MINNESOTA.

(Batostoma humile.

occasionally appearing subsolid. Acanthopores numerous, rather small, often indent-
ing the zoecial apertures. Interspaces variable, occupied by closed mesopores, often
thinner and the zoccial walls more in contact with each other than shown in fig. 27.
About ten zocecial apertures in 3 mm.

None of the specimens at hand have preserved the internal characters in a fully
satisfactory manner. The sections prepared, however, are sufficiently clear to make
the generic reference of the species unquestionable. They point, furthermore, to
close relationship with B. varium, differing from that species in having the periph-
eral region narrower and diaphragms less abundant. Of external peculiarities the
possession of well marked monticules distinguishes the species from ‘all related
forms. For comparisons with associated monticulose species belonging to other
genera see p. 227. . ‘

Formation and locality—Not uncommon in the upper third of the Trenton shales at Poe’s farm,
near Cannon Falls, Minnesota.

Mus. Reg. No. 8134.

BarTosToMA HUMILE, 2. sp.

”

PLATE XXV, FIGS, 29-36,

Zoarium rather small, consisting of comparatively slender, compressed or sub-
cylindrical branches, 4 to 11 mm., commonly 5 to 7 mm., in width; bifurcations few,
less frequent than usual with species of this genus; surface without monticules, but
more or less strongly spinulose in the older stages. Zocecial apertures subovate,
varying in size according to thickness of walls and interspaces, generally with a
thickened rim; apertures subequal, eight or nine in 8 mm. Interspaces variable,
depressed, the zocecial walls sometimes in contact at as many points as the rounded
form of the tubes will admit; more commonly their walls are completely separated.
At intervals the interspaces may widen and form subsolid spots. Acanthopores
numerous, situated in the interspaces or on the outer side of the walls, small and
often difficult to distinguish on young examples, but conspicuous enough on well
matured specimens and very much so on several apparently old fragments. In the
latter the interspaces may be solidified and raised instead of depressed, and the
size of the zocecial apertures 0.15 by 0.2 mm. against 0.2 by 0.8 mm. in young
specimens.

Internal characters: Good tangential sections cannot be prepared except from
fully matured or old examples, because of the brevity of the peripheral region.
Young specimens give tangential sections like the upper half of fig. 33, With thin
walls and angular zocecia. With age the walls become thickened, ring-like and
BRYOZOA. 295

Batostoma winchelli.]

more or less separated by partially filled mesopores. The acanthopores also increase
in size and distinctness but, being situated either in the interspaces or on the outer
side of the zocecial walls, never encroach upon the zocecial cavities. In the axial
region of vertical sections the tubes have irregularly undulating thin walls and no
diaphragms. Nor are these structures developed except in the unusually narrow
peripheral region, where from one to three have been observed in each tube. The
mesopores are very short and provided with two or three thick diaphragms; or they
may appear to be filled with solid tissue.

The oval zocecial apertures, more slender growth, and absence of monticules
are the most striking differences between the present species and B. montuosum.
The zoarium is smaller, the branches more slender, and the peripheral region much
narrower than in B. varium. An undescribed variety of B. jamesi Nich. sp., occurring
in the Utica horizon at Cincinnati, Ohio, corresponds more nearly than any of the
known Minnesota species of the genus.

Formation and locality.—Moderately abundant in- the Galena shales at St. Paul and near Cannon
Falls, Minnesota. Aiso at Decorah, Iowa. A similar, perhaps identical, species occurs in the Trenton
of central Kentucky.

Mus. Reg. Nos. 7613, 8063.

BatTosTtoMA WINCHELLI Ulrich.
PLATE XXVI, FIGS. 33-37; PLATE XXVII, FIGS. 1-6.

Amplexopora winchelli ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 91.

Zoarium irregularly ramose; branches subcylindrical or a little compressed,
varying in diameter from 4 to 10 mm., but in nine-tenths of the fragments seen from
5to7 mm. In the typical and common form of the species monticules are wanting,
nor are the clusters of apertures of larger size than the average, which sometimes
take their place, ever a conspicuous feature. Occasionally they are rendered more
distinct than usual by a thickening of the interspaces and an aggregation of the
mesopores. In a variety that may be distinguished as nodosa, the surface is thrown
up into more or less strongly marked monticules. Zoccial apertures rounded
or subangular, rather irregularly arranged, ten to twelve in 3mm.; walls moderately
thick in most specimens, comparatively thin in young, very thick in worn old ones,
ridge-shaped when perfect, and with acanthopore spines at nearly all angles of
junction. Mesopores sparingly developed, never as numerous as the zocecia, occur-
ring chiefly in small straggling clusters, their mouths open, of various sizes, some of

them apparently developing into zooecia.
296 THE PALEONTOLOGY OF MINNESOTA.

{Batostoma winchelli.

Internal characters: Being an exceedingly common and superficially variable
species, over thirty sets of thin sections were prepared. These prove the species
constant in most of the characters shown in vertical sections, and decidedly variable
in tangential sections. It should, however, be stated that many of the specimens
sectioned exhibited some external peculiarity or deviation from the ordinary types
of the species. In the axial region of vertical sections the tubes are thin-walled
and crossed by diaphragms from one to three times their diameter distant from
each other. But in the attenuate proximal ends of the tubes the diaphragms are
always closer than after the tubes have attained their full size. In entering the
peripheral region, the width of which depends upon age, the tubes bend outward
rather abruptly, proceeding thereafter directly to the surface. In the turn the
diaphragms become more numerous and, though generally straight and complete,
not infrequently exhibit a tendency to coalesce with each other. In the mesopores,
which sometimes evidently changed into zocecial tubes, the diaphragms occur
regularly seven in 0.5 mm.

In figs. 4to 8 on plate XXVII, I have endeavored to Rae the principal
variations noticed in tangential sections. The most of them are as in fig. 6, and
figs. 4 and 5 represent what I regard asa condition of extreme age, differing from the
usual condition merely in having an extra internal deposit of hard tissue. Figs. 7
and 8, however, deviate in a more important respect in having stronger and more
abundant acanthopores. Many of these, furthermore, are developed between the
angles, causing an inbending of the tube-walls. The average size of the zocwcia
in this form, which may receive the provisional name of var. spinulosum, is also a
trifle greater than usual.

The systematic position of this and the two species following is somewhat
doubtful, but after careful reflection I have selected Batostoma as more fitting to
receive them than Amplexopora. The closer tabulation of the proximal ends of the
tubes, the irregularity of the tubes in the axial region, and their division there (as
seen in the central part of transverse sections) into a large and small series, are
characters so far unknown in Amplexopora. But my chief reason for placing the
species with Batostoma is found in the marked resemblance exhibited by fig. 8 to
similar views of B. implicata and B. jamesi of the Cincinnati rocks.

Formation and locality. —Very abundant in the middle third of the Trenton shales at St. Paul,
Minneapolis, and localities in Goodhue and Fillmore counties, Minnesota.

Mus. Reg. Nos, 5999-6001, 8092, 8095,
Batostoma minnesotense.]

BRYOZOA. 297

BaTOsTOMA MINNESOTENSE, 7. sp.
PLATE XXVI, FIGS. 38-40; PLATE XXVII, FIGS, 9-15.

Amplexopora superba ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 92.
(Not Foord, 1883, Cuntri. Micro-Pal. Cambro-Sil. Rocks, Can., p. 16.)

Zoarium ramose, above the medium size for the genus; branches without mon-
ticules, subcylindrical, bifurcating at rather long intervals, averaging 9 or 10 mm.
in diameter, but varying between the extremes of 7and 15mm. Zoccial apertures
subangular, with walls of moderate thickness, arranged in regular curving series
about clusters of orifices that are in most cases decidedly larger than the average;
of the latter sometimes nine, more often ten, occur in 3mm. Prominent acantho-
pores at all the angles of junction, and in many cases another is placed between the
angles. These at all times occupy the summit or center of the walls and in no case
cause irregularities in the form of the zocecial apertures. Mesopores very few,
scattered at random among the larger apertures.

Internal characters: In tangential sections the walls are nearly uniformly thick,
with the angles of junction often appearing as open (pl. X XVII, fig. 15). In other
cases the angles are occupied by dark spaces louking more like the usual appearance
of acanthopores. A more typical phase of the species is shown in figs. 9 and 10,
representing parts of a section of an excellently preserved example. In this we
have more abundant acanthopores and the cavity in these is unusually large, while
many of the angles are occupied by open spaces similar to those shown in fig. 15.

In vertical sections the tubes are provided with thin wavy walls in the axial
region, where they are also a little irregular and generally entirely without dia-
phragms, the latter first making their appearance as the tubes bend into the
peripheral region. In the outer region the walls are much thickened and in places
distinctly traversed longitudinally by acanthopores. The mesopores are but seldom
observed, have few diaphragms and appear to be in part filled with solid tissue. The
arrangement of the diaphragms in the zocecial tubes varies somewhat in different
sections. Figures 11 and 18 represent extremes in this respect.

This species, though closely related to B. winchelli, is readily distinguished
externally by its larger size and slightly larger and more regularly arranged zocecial
apertures; internally by the wavy walls and the absence of diaphragms in the axial
region. Foord’s Amplexopora superba, to which I at first referred this species, is
probably congeneric, but distinguished specifically by having nearly straight instead
of wavy walls to the axial tubes, and a tuberculated surface.

Formation and locality.—Not rare in the middle third of the Trenton shales at Minneapolis, St.
Paul and other localities in Minnesota.
Mus. Reg. Nos. 5996, 5998, 7592, 7668, 8093,
298 THE PALEONTOLOGY OF MINNESOTA.

[Batostoma? decipiens.

BaTOSTOMA? DECIPIENS, ”. Sp.

PLATE XXVII FIGS. 16-19,

Zoarium ramose, branches smooth, 5 to 12 mm. in diameter. Zocecia with
moderately thick walls; apertures polygonal, subequal, about eleven in 3 mm.
When in a good state of preservation the walls are sharply ridge-shaped, appearing
thinner than ‘usual. Clusters of large cells scarcely distinguishable. Mesopores
very few, acanthopores not observed at the surface.

Internal characters: Vertical sections show that in the axial region the proximal
end of the tubes is crossed by four to six diaphragms, 0.2 mm. or less apart. Above
these the distance between them is from two to four times as great until the tubes
are about to turn into the well defined peripheral region, when their number is
greatly increased. In the outer part of the tubes, where the diaphragms also
exhibit a tendency to coalesce, the number varies in different sections from seven
to twelve in 0.5 mm.

In tangential sections the walls are thick, though some difference in this respect
is noticeable in the ten sets of sections prepared. This is owing to the varying
thickness of the internal concentrically laminated deposit. The divisional line
between adjoining tubes is sharply marked, and sometimes contains a small,
acanthopore-like dot midway or thereabout between the angles of junction. The
mesopores, which are scattered very sparingly among the zoccia, and sometimes
gathered into clusters of three or four, look very much as though they might be
merely young or perhaps aborted zocecia, differing from them, so far as can be seen
in these sections, solely in the matter of size.

The systematic position of this species cannot be determined finally until we
know more of the Chazy Trepostomata. Without that knowledge its affinities appear
to lie as closely with B. winchelli on the one hand as with Callopora angularis on the
other. I thought much of classing the species with Callopora, but at last concluded
that the occasional presence of acanthopores and greater thickness of the walls
would not now admit of such an arrangement. Callopora angularis, which of all the
associated species is probably the most like B.? decipiens, has smaller branches and
thinner zocecial walls.

Formation and locality.—Rather rare in the lower and middle third of the Trenton shales at Min-
neapolis, Minnesota.
BRYOZOA. 299
Hemiphragma.]

Genus HEMIPHRAGMA, n. gen.

_Batostoma (part.) ULRIog, 1890. Geol. Surv. Ill, vol. viii, p. 379.

Zoaria like those of Batostoma save in this, that the diaphragms in the periph-
eral part of the zocecial tubes are incomplete.

Type: Batostoma irrasum Ulrich.

The discovery of a fourth species having incomplete diaphragms has decided
me in giving the character generic rank. What may prove to be a fifth species,
occurs among my material from the upper beds of the Hudson river group at
Delafield and Tron Ridge, Wisconsin. Unfortunately, the Bryozoa which occur so
abundantly at those localities do not preserve the internal characters, so that in
cases like this it is impossible to verify the generic affinities of the species by means
of thin sections. It is possible that the natural relations of Hemiphragma are not

with Batostoma, but in the absence of data showing the value of the difference be-
tween the two genera, we are obliged to place them together because of their
marked agreement in all other respects.

HemirpHrRaGMA rrRASsUM Ulrich.
PLATE XXIV, FIGS. 5-19.

Batostoma irrasa ULRICH, 1886. Fourteenth Ann. Rept. Geo. Nat. Hist. Sur. Minn., p. 94.

Zoarium consisting of small, subcylindrical, frequently and rather irregularly
dividing branches, commonly 5 or 6 mm. in diameter, but varying from 4 to 8 mm.,
the latter extreme probably only when an extra layer of tubes has grown over the
original branch. Monticules wanting, but under fully matured conditions the sur-
face is abundantly spinulose. Zocecia with subangular apertures and thin walls
when young, and with smaller, subcircular or oval apertures and more or less thick
walls in fully matured examples; arrangement of apertures rather regular in rows
about small solid spots, in the immediate vicinity of which the zowcia may be of
larger size than elsewhere; seven to nine in 3 mm. Interspaces apparently solid
and generally with shallow irregular depressions in most specimens, but in very
young stages a variable number of irregular mesopores may be recognized. Acan-
thopores numerous, two or more to each zocecium, situated in the angles of junction
and interspaces, and increasing in size with age. They are large and a conspicuous
external feature of well preserved mature examples.

Internal characters - In the axial region of vertical sections the tubes have thin
and irregularly fluctuating walls, and few or no diaphragms. The latter are com-
plete here and the proximal end of the tube expands to full size with unusual
300 THE PALEONTOLOGY OF MINNESOTA.

(Hemiphragma ottawense.

rapidity. In the peripheral region, which is narrow and abruptly distinguished
from the axial, the walls are more or less thickened, and the tubes intersected by
semi-diaphragms, about four in 0.5 mm. I have satisfied myself that all the trans-
verse partitions in this outer part of the zoccial tubes are really incomplete. That
many may appear entire in sections is only because their inner edge happens to be
vertical instead of horizontal. Mesopores are difficult to make out in these sections,
being short and usually filled, in part at least, with solid tissue. Tangential sections
require no description, all the essential characters being shown in figs. 6, 7, 9 and 14.
In the axial part of transverse sections the tubes are unusually irregular and their
walls comparatively thick. *

This is a common and well marked species, but proves to be nearer H. ottawense
Foord sp., than I thought at first. Perhaps the only reliable difference, and that
may in part be due to the greater size of Foord’s species, is the much smaller num-
ber of diaphragms in H. irrasum. The largest specimens of the latter even do not
approach ZH. ottawense in the width of the closely tabulated peripheral region.

Formation and localityx—Common in the lower third and rare in the middle and upper thirds of
the Trenton shales at Minneapolis, St. Paul, and Preston. In the overlying Galena shales it is
again common at St. Paul and at various localities in Goodhue county. Also at Decorah, Iowa.

Mus. Reg. Nos. 7618, 7627, 8033, 8041, 8051, 8078.

HEMIPHRAGMA OTTAWENSE Foord.
PLATE XXIV, FIGS. 1-4,

Batostoma ottawense FooRD, 1883. Contri. to Micro-Pal. Cambro-Sil. Rocks, Can., p, 18.

This species is so much like the preceding that it is sufficient to merely point
out the differences between them. In the first place H. ottawense is always of larger
size than H. irrasum, the width of its branches, which in some cases are strongly
compressed, varying from 9 to over 30 mm., and their thickness from 8 to 12 mm.
Internally, the axial region is comparatively smaller and the tubes here have dia-
phragms which, though sometimes wanting for short distances, are yet more abund-
ant throughout the region than in H. irrasum. In the latter the peripheral region
is narrow and the number of semi-diaphragms correspondingly limited. In the
present species, however, this region is wide and the number of cross-partitions
often great. The difference in these respects is generally quite as marked as in
figures 3 and 5 on plate XXIV.

Foord says of the Canadian form of the species (loc. cit.) that the surface exhibits
“small and inconspicuous monticules placed at variable distances apart and occu-
pied by from ten to fifteen cells slightly larger than the average.” The monticules
BRYOZOA. 301

Hemiphragma tenuimurale.]

are wanting in the specimens collected by me at Ottawa and in the Minnesota form,
but smooth spots, consisting of clusters of mesopores, are present instead, and in
the immediate vicinity of the spots the zocecial apertures are larger than midway
between them. It is possible that Mr. Foord was mistaken in crediting the species
with monticules, since these spots, being more solid than the rest of the zoarium,
are likely to withstand weathering better and thus to appear gradually as elevated
points.

Formation and localityx—In Minnesota the species is rather rare and restricted to the upper part
of the Galena shales at Kenyon, Berne and Mantorville.. The same horizon contains Fusispira ventricosa
Hall, Orthis germana W. and S., Pachydictya pumila, Homotrypa similis, Monotrypa (? Chetetes) cumulata,
and other highly characteristic fossils.

Mus. Reg. No. 6002.

HEMIPHRAGMA TENUIMURALE, 7. SD.

PLATE XXIV, FIGS 20-23.

In its growth and general aspect this species is precisely like H. irrasum. Under
a hand lens, however, they are immediately distinguished by the much thinner walls,
fewer mesopores, and seeming total absence of acanthopores in the present species.
In H. irrasum the zocecial apertures also are always of rounded form, in H. tenuimurale
angular. These differences, as may be seen from figs. 5 to 8 and 20 to 22 of plate
XXIV, are no less obvious when we compare the internal characters of the two
species. It is true, perhaps, that we may occasionally see faint evidence of very
small acanthopores at the angles of junction in tangential sections, yet they are too
indistinct and small to compare with the acanthopores of H.irrasum. In tangential
sections the species is much more like H. imperfectum (Batostoma imperfectum Ulrich)
of the Hudson river group of Illinois and Wisconsin. But that species grows to a
much greater size and has rather conspicuous clusters of mesopores. H. ottawense,
besides being much larger and having more abundant semi-diaphragms, differs in
the same manner as H. irrasum.

Formation and locality—Not uncommon in the Galena shales at various localities in Goodhue
county, Minnesota.
Mus. Reg. Nos. 8032, 8042, 8052.

Genus STROMATOTRYPA, n. gen.

Zoarium consisting of one or several superimposed thin layers growing upon
foreign bodies. Zocecial tubes short, with few diaphragms, the proximal end
scarcely prostrate, oval in cross-section; walls thin, containing periodically con-
stricted, bead-like tubuli (? modified acanthopores), one or more to each zocecium.
302 THE PALEONTOLOGY OF MINNESOTA.

_[Stromatotrypa ovata.

Apertures oval, separated by depressed interspaces, the peristomes minutely papil-
lose. Mesopores abundant, beginning on the basal lamina, decreasing in size with
age, closely tabulated, the diaphragms finely punctured; mouths rarely visible,
closed by a common dermal sheet. True acanthopores wanting.

Type: Stromatotrypa ovata, n. sp. :

The species upon which this genus is based has much to remind us of the
Devonian Pinacotrypa, Ulrich. But as that genus is clearly a branch of the Fistuls-
poride, and Stromatotrypa most likely not far removed from Batostoma and Tremato-
pora, it is evident that there can be no real affinity with Pinacotrypa. The
arrangement with the Diplotrypide, though provisional, is strongly suggested by
the dimorphic character of the zoarium and the supposed relationship to Bastos-

toma.

STROMATOTRYPA OVATA, ”. Sp.

PLATE XXIV, FIGS. 24-31.

Zoarium consisting of one or more exceedingly thin layers, varying in thickness
from 0.5 to 2.0 mm., occasionally attached to shells, but more commonly encrusting
other Bryozoa. Sometimes the attachment is incomplete, and in a few cases the
zoarium is free, with the underside wrinkled. Surface without monticules, but
exhibiting at irregular intervals smooth spots of greater or less extent on which
the zocecia are generally farther apart than usual and the apertures of some of them
closed. Zocecial apertures oval, peristomes thin, in contact at limited points or more
or less widely separated, the arrangement inclining to be irregular, with six to eight,
commonly seven, in 8 mm.; length of apertures varying from 0.3 to 0.45 mm., the
average about 0.28 by 0.88 mm. Interspaces depressed, of variable width, apparently
smooth in the youngest stages, minutely granulose in the aged conditions. Small
acanthopore-like elevations generally where peristomes come into contact. The
best preserved specimens exhibit also a row of minute papille crowning the peri-
stomes. ?

Internal characters: In tangential sections the zoccial walls are thin and in
contact at one or more points, or they may be completely isolated by mesopores
varying considerably in shape and size. Attached to the walls, or more frequently
occupying the angles of junction, are minute rounded and thin-walled cells that are
perhaps to be regarded as peculiarly modified acanthopores. Good sections show
besides a large number of smaller dots in the interspaces and zocecial walls. In
vertical sections both sets of tubes rise abruptly from the basal lamina, and the
mesopores decrease more or less conspicuously in size in nearing the surface.
BRYOZOA. 303
Monotrypa.]

Diaphragms are few in the zocecial tubes, but in the mesopores, which are usually
constricted at the point of crossing, they are abundant. Here and there the zoccial
walls seem to diverge periodically so as to produce minute beaded tubuli.

There is no parasitic bryozoan known to me from Lower Silurian rocks with
which this species could be confounded. Ramose Bryozoa coated with it might be
mistaken for certain varieties of Batostoma fertile, but the crusts-are rarely complete
enough to render such a difficulty common. A greater superficial resemblance even
is sometimes presented to young examples of Pachydicta foliata, a truly bifoliate
species, with very different internal structure and really so distinct that no one
ought ever to confuse them. .

Formation and locality—Not uncommon in the lower and middle thirds of the Trenton shales at
Minneapolis and St. Paul, Minnesota. Occurs also in the ‘‘ Lower Blue” at Beloit, Wisconsin. :

Genus MONOTRYPA, Nicholson.

Monotrypa (part.), NICHOLSON, 1879, Pal. Tab. Cor., p. 293; 1881, Genus Monticulipora, pp. 102 and
168; ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 153; Foorp,
1883, Contri. Micro-Pal. Can., p. 14.

Monotrypa, ULRICH, 1890. Geol. Surv. Ill., vol. viii, p. 379.

Ptychonema, HAuL, 1887. Pal. N. Y.; vol. vi, p. xiii.

Zoaria irregularly massive, discoid, or subglobose, apparently not divisible into
‘mature and immature regions. Zoccia comparatively large, prismatic, with very
thin, straight or transversely wrinkled walls; diaphragms complete, remotely placed
in the tubes. Both mesopores and acanthopores wanting.

Type: M. undulata Nicholson.

We are satisfied that thé position of this genus is near Diplotrypa (sensu stricto)
and the simple section of the genus Batostoma. In the last we have only the ramose
habit of growth, and few and small mesopores and acanthopores to distinguish it
from Monotrypa, the structure of the walls and the character of all the other points
being precisely the same in the two groups. In Diplotrypa diaphragms are perhaps
always more abundant, but in all other respects, excepting that the tapering prox-
imal ends of the zocecial tubes are closely tabulated like mesopores, the structure is
essentially the same as in Monotrypa. There is a largeness and a certain looseness
of arrangement that distinguishes the whole family Diplotrypide from the Amplexo-
poride, a family including (under Leptotrypa) a number of simple species agreeing
otherwise closely with Monotrypa. These species of Leptotrypa (e. g. L. filiosa d’Orb.
sp. and L. petasiformis Nich. sp.) belong, I am convinced, to a different line of devel-

opment than that of true Monotrypa.
304 THE PALEONTOLOGY OF MINNESOTA.

(Monotrypa magna.

The genus as restricted embraces but few species. Besides the type, which
occurs in the Trenton of Canada and New York, we have M. subglobosa Ulrich, in
the Utica horizon at Cincinnati, M. rectimuralis Ulrich, in the Trenton of southern
Illinois and probably in the Cincinnati group of Ohio, M. intabulata, n. sp., and M.
(? Cheetetes) cumulata, n. sp., in the Galena of Minnesota, M. magna, n. sp., in the
Birdseye limestone of the northwest, M. colliculata (Chetetes colliculatus Hall,) in the
Lower Helderberg of New York, and M. tabulata (Ptychonema tabulatum Hall,) in the
Upper Helderberg of New York. A small undescribed species vccurs in the Niagara
of Indiana, while another, apparently belonging here, I found in the Corniferous
limestone at Columbus, Ohio.

MonoTrRyPA MAGNA, 2. Sp.

PLATE XXVII, FIGS. 28 and 29. ~

Zoarium growing in large expanded masses, sometimes consisting of superposed
layers, the whole perhaps 20 to 40 mm. high and 100 mm. wide; under side generally
with a wrinkled epitheca, the upper celluliferous and without monticules. Zocecia
large, polygonal, thin-walled, with clusters of larger size than the average at inter-
vals of about 6 mm., measuring from center to center; about nine in 5 mm.; size of
largest in the clusters about 0.8 mm., average diameter of these in the spaces between
the clusters about 0.5 mm.

Internal characters: In vertical sections the zocecial walls are strongly undulat-
ing and very thin throughout, and the tubes crossed by complete horizontal dia-
phragms at intervals varying between one and three times the diameter of a tube.
Transverse sections exhibit thin structureless walls, an occasional small (young)
cell, and a total absence of mesopores and acanthopores.

The larger size of the zocecia distinguishes the species from M. undulata Nichol-
son. Excepting the Crepipora perampla of the present work, they are larger than in
any paleozoic bryozoan known to me. The zoaria of that species are comparatively
higher and less expanded, and their zocecia provided with lunaria.

Formation and locality.—Not uncommon in the ‘‘Lower Blue” limestone at Dixon, Illinois; also

at Mineral Point and Beloit in Wisconsin. A small fragment from the equivalent limestone at Minne-
apolis is provisionally identified with it.
BRYOZOA. 805

Monotrypa intabulata.]

MonoTRYPA INTABULATA, 7. sp.

Compare Monotrypa rectimuralis ULRICH, 1890, Geol. Sur. Ill, vol. viii, p. 462.

 

Fie. 20. Monotrypa intabulata, n. sp. Upper half of Galena shales, Goodhue and Fillmore counties,
Minnesota. Collection of E.O. Ulrich. a, transverse section, x18, showing subequal size of tubes, their
thin walls, and the lucid spot in the angles of junction; b, vertical section, x18, the tubes filled chiefly
with clayey matrix; c, trarisverse section, x18, of a variety from Fountain, Minnesota, provisionally
referred to this species. It has larger zocecia than usual, while the size of the latter seems also to be
rather less equal.

Zoarium forming subhemispherical or depressed-spherical masses, generally
between 30 and 60mm. in diameter and 15 to 30 mm. in hight; lower surface
usually less convex than the upper and sometimes partly covered by an epitheca.
Celluliferous surface even, covered with subequal, thin walled, polygonal zoccial
apertures, of which the usual number in 3 mm. is between eight and nine. In sev-
eral small examples found near Fountain, the number is between seven and eight.
Conspicuous ‘and regularly arranged clusters of large cells are wanting, though here
and there one or several zocecia may be of unusual dimensions. _

Internal characters: In transverse sections the walls are exceedingly thin, but
where well preserved their duplex character is determined by minute triangular,
seemingly open spaces at the angles of junction, formed by the separation of the
walls of adjoining tubes. Here and there a young zoccium is met with, but true
mesopores and acanthopores as well, are unquestionably wanting. In vertical sec-
tions the walls form nearly straight lines (merely curving to adapt themselves to the
growth of the zoarium) being entirely without the crenulations so characteristic of
the typical species of the genus. Diaphragms also seem to be wanting, and most of
the tubes of specimens from shaly strata are in great part filled with the matrix.

At first I believed this species must be the same as the M. rectimuralis Ulrich,
the types of which were collected from nearly equivalent beds in southern Illinois.
The absence of diaphragms was explained by the supposition that they had been

—20
806 THE PALEONTOLOGY OF MINNESOTA.

{Monotrypa nodosa.

destroyed during the process of fossilization. But the study of new material, and
other sets of thin sections shows that this explanation is inadequate, since, while
the diaphragms are always absent in this form they are present in all associated
Bryozoa; and it stands to reason that the conditions under which the two sets of
specimens were preserved must necessarily have been identical. I am obliged there-
fore to consider their absence in the Monotrypa as normal, and to give these peculiar
Minnesota specimens a new name.

M. intabulata agrees with M. rectimuralis* not only in the external appearance of
the zoarium but in having straight walls and minute triangular open spaces at the
angles of junction as well. As differences we have diaphragms two to four times
their diameter apart, and rather conspicuous clusters of large cells in the latter and
none in the former.

Among associated forms only Monticulipora grandis and Bythotrypa laxata have
a similar growth, the species of Prasopora and Mesotrypa forming discoidal zoaria.
Both of these species however are too widely different structurally from Monotrypa
to be confounded. .

Formation and locality.—Not uncommon in the upper part of the Galena shales (Fusispira beds)
at several localities in Goodhue and Fillmore counties, Minnesota.

Mus. Reg. No. 8379.

MonoTryPa NODOSA, 7”. Sp.
(Not Figured.)

Monticulipora (?) ortoni WHITFIELD, 1882. Geol. Wis., vol. iv, p. 251. (Not Cheetetes ortont NICHOL-
SON, 1875. Pal. Ohio, vol. ii, p. 211.)

Zoarium commonly beginning its growth upon shells over and beyond which
it spreads till it forms large discoidal or hemispheric masses, often over 5 or 6 cm. in
diameter. Sometimes the masses are shapeless, but as a rule the base is concave,
and, where it projects beyond the covered shell, clothed with a wrinkled epitheca.
Upper surface with more or less prominent subconical monticules, averaging about
3.4mm. from summit to summit. Zocecia with thin walls, polygonal and ‘rather
regularly arranged apertures, nine or ten in 3 mm.; apertures occupying the mon-
ticules but little if at all larger than those in the intermediate spaces. Summits of
monticules occasionally appearing solid. Not a trace of either mesopores or acan-
thopores has been observed. Internal characters unknown, none of the specimens
seen being fit for sectioning.

 

 

*In the original description of the species I included, erroneously, a hemispheric or lenti@ular, tuberculated form that is
very common in the Hudson river rocks at Savannah, Illinois, and Delafield and Tron Ridge, Wisconsin. As it may justly be

expected to occur in the southern part of Minnesota, the next brief description of its known characters may be of advantage
to students of the paleontology of the State.
BRYOZOA. 307

Monotrypa (? Chatetes) cumulata.]

In the absence of any knowledge of the interior the generic position of the
species is necessarily a little doubtful. In a general way, M. nodosa resembles
Leptrotypa filiosa Orb. sp., of a lower horizon in the Hudson river rocks, very closely,
and the principal difference that can now be pointed out is in the size of the zoccia,
that species having eleven or twelve apertures where the present form has nine or
ten. But Atactoporella ortoni Nich. sp., to which Whitfield referred the Wisconsin
specimens, is a delicate parasitic form totally distinct.

Formation and locality.—Common in the upper beds of the Hudson river group at Iron Ridge and
Delafield, Wisconsin, and Savannah, Illinois.

Mus, Reg. No. 7574.

Monotrypa (? CH&TETES) CUMULATA, 2. sp.

“PLATE XXVII, FIGS. 26 and 27.

Zoarium forming small subglobular or irregular masses, generally consisting
distinctly of irregularly superposed layers ; average sizes between 15 and 20 mm. in
diameter, anything under or over those extremes being rare; no monticules.
Zocecial walls thin; apertures polygonal, of unequal sizes, sometimes forming at
long but irregular intervals large clusters in which they are conspicuously larger
than elsewhere ; in most cases however the apertures are subequal, with an average
of six and one-half or seven in 3mm. Mesopores and acanthopores wanting.

Internal characters: In vertical sections the tubes diverge rapidly and rather
irregularly, and their walls present an obscure longitudinal lineation. Diaphragms
occur at intervals varying from one to four times their diameter, but their position
in neighboring tubes corresponds approximately. In transverse sections the prin-
cipal interest attaches to the structure of the walls. In most sections the wall
is comparatively thick and seems to be composed of minute columns which, being
cut transversely, appear as alternately dark and lighter parts. In this respect the
structure of the walls is essentially the same as in true Chetetes, and I would un-
hesitatingly have placed the species into that genus had I been able to satisfy
myself that the phenomena observed were not the result of secondary causes.
Namely, in some sections the appearance is very different, the wall itself being more
sharply defined and thinner than usual (especially where the tubes are filled with
matrix instead of calcite) and without the alternating light and dark spots. But
where the tubes are filled with calcite the latter for some distance inward from the
wall is of a darker color than at the center, and exhibits, strange to say, a spotting
not unlike that pertaining to the wall itself in other sections.
308 THE PALEONTOLOGY OF MINNESOTA.

[Trem atoporidz

The external form, though smaller, is much the same as in M. intabulata and
other species of the genus, but the zocecia are larger, and none of them have a wall-
structure as described above.

Formation and locality.—Upper part of the. Galena shales (Fusispira beds) at various localities in
Goodhue county, Minnesota. Also in the Trenton limestone of Canada.

Mus. Reg. Nos. 7629, 7635, 8026.

Family TREMATOPORIDA, Ulrich.

For remarks on this family see p. 289.

a

Genus TREMATOPORA, Hall.

Trematopora, HALL, 1852, Pal. N. Y., vol. ii, p. 149; DyBowsk1I, 1877, Die Chetetiden, p. 69;
ULRIcH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p, 241; 1883, ¢dem.,
vol. vi, p. 257; HALL, 1887, Pal. N. Y., vol. vi, p. xiv; ULRICH, 1890,
Geol. Surv. Ill, vol. viii, pp. 373, 418.

Not Trematopora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 153.

Zoaria ramose, branches solid, even or montiferous. Zocecia with oval or sub-
circular apertures; surrounded by more or less elevated peristome. Interspaces
depressed, sometimes exhibiting the closed mouths of the abundant mesopores.
Zocecial tubes with thin walls and few diaphragms. Mesopores irregularly angular,
generally exhibiting an obscurely beaded appearance in vertical sections, with a
diaphragm at the constriction. Acanthopores superficial, of moderate or small size,
one or more to each zocecium. cE

Type: T. tuberculosa Hall, Niagara group. A

The really essential characters of this genus have been most persistently misin-
interpreted and overlooked. Even now lam not satisfied that they are fully brought
out in the above diagnosis, which is practically the same as the one in volume viii of
the Illinois reports. The truth is that more study, especially genealogical, is required
before it will be possible to delineate even approximately the limits of the genus.
Thus, while almost certain that most of the Lower Silurian species placed here by
me (¢. g. T. primigenia and T.? nitida) are not really related to T. tuberculosa, I find
myself unable as yet to justify their placement elesewhere.

As stated on a preceding page (289) the type of the genus presents many points
of agreement with Batostoma and is probably to be viewed as a later expression of
the same type of structure. Not so, however, with T.? primigenia and allied species,
these being much more like Leioclema, Bythopora and Batostomella, on the one hand,
Trematopora? primigenta.} BRYOZOA. ay
and Nicholsonella and Constellaria on the other. And yet, above all, there are pecu-
liarities that postpone the determination of the systematic position of the next
following species till we can learn something of their ancestors. In the meantime
they can remain under Trematopora and their doubtful affinities be indicated by the
usual sign.

As regards Trematella and Orthopora, two subgeneric names proposed by Hall,*
the first is clearly a synonym for Batostomella, Ulrich, the second for Rhombopora,
Meek. Both groups are widely different from true Trematopora.

TREMATOPORA? PRIMIGENIA Ulrich.
PLATE XXI, FIGS. 23-40.

Trematopora primigenta ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 97.

Zoarium loosely bushy, consisting of small slender ramulets, dividing dichotom-
ously at varying intervals; branches cylindrical or compressed, commonly about 2
mm. in diameter, but varying from 1.5 to 4.0 mm., arising in greater or lesser num-
bers from a large basal expansion that is thinly spread over some cylindrical body
like a. crinoid column. Not infrequently the branches inosculate freely. Entire
zoaria varying in diameter probably between 20 and 60 mm. Superficial aspect of
zocecia varying with age. In young stages or examples the apertures are more or
less oblique, with only the posterior border elevated and the interspaces in a varying
degree narrower than the apertures. With age the apertures become somewhat
smaller, ovate or subcircular and direct, and the peristome or rim equally elevated
all around, while the interspaces were widened till in some examples they are often
equal to twice the width of the zowcial orifices. At the same time the interspaces,
which as a rule exhibit no sign of the really very numerous mesopores, are roughened,
as are also the peristomes, by the development of acanthopores. These vary greatly
in size and number. The arrangement of the zoccial apertures is only moderately
regular, there being here and there spots in which they are of larger size and more
widely separated than usual. An average of twelve or thirteen in 3 mm., but the
number in that distance may vary from eleven to fifteen.

Internal characters: In vertical sections the tubes have thin walls, are not
entirely vertical, and without diaphragms in the axial region. Near the surface
they bend outward rather abruptly when one and sometimes two diaphragms were
in most cases thrown across each tube. At the same time an abundant series of
mesopores was developed. These are crossed by from two to six diaphragms, the

 

*Pal, N. Y., vol. vi. p. Xiv, 1887.
310 THE PALEONTOLOGY OF MINNESOTA.

(Var. ornata.

outer ones of which are much thicker and separated by shorter intervals than the
inner pair. This gradual thickening of the diaphragms is more decided in the
branches than in the basal expansion, part of a vertical section of which is rep-
resented in fig. 40. The walls of the mesopores where two or more occupy an inter-
space are strongly zigzag, in some instances appearing not unlike vesicular tissue.
In tangential sections the zocecial walls may be thin and occasionally even inflected
by the acanthopores (fig. 37), but as a rule they are ring-like, as in figs. 38 and 39, and
generally completely separated from each other by a series of unequal and irregu-
larly shaped mesopores. The acanthopores are distinct, nearly uniform in size,
usually attached to the outer side of the zocecial walls, and number from one to

three or four to each zocecium.

Var. ornata Ulrich.
PLATE XXI, FIGS. 26, 28, 33, 34.

Trematopora ornata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 98.

Increased collections have convinced me that this is merely an uncommon
variety of T.? primigenia, differing from the typical form of the species, as above
described, in having the zocecial apertures a little more elongate and rather more
regularly arranged, and in having the peristomes crowned by a crowded row of
small papilla. Larger spines, as shown in fig. 34, are sometimes present.

Var. SPINOSA, 7. var.

PLATE XXI, FIGS. 29, 30, 35, 36.

Of this form, which, if it proves permanent, should be called a species, I have
seen only a few specimens. Though evidently mature they are a trifle smaller than
typical 7. ? primigenia, and differ in a number of other minor points from that form:
But their principal peculiarity, and the only one that in the present state of our
knowedge deserves mention, is the presence of a considerable number of strong
spines in the interspaces. A few smaller acanthopores are scattered among the
larger ones, but unless searched for they are likely to be overlooked.

The large basal expansion, small branches, rounded zoccial apertures and
depressed interspaces are features that serve to distinguish this species and varieties
at once from all associated ramose Bryozoa.

Formation and locality.—The typical form is an abundant fossil in the middle third of the Trenton
shales at St. Paul and Minneapolis, while it is not uncommon in the same beds at other localities in the
State, notably near Fountain and Preston in Fillmore county. The two varieties are rare and associated
with the typical form at St. Paul and vicinity.

Mus. Reg. Nos. 6010, 6011, 7654, 7661,
~ BRYOZOA. $11

Constellariaj

Genus CONSTELLARIA, Dana.

Constellaria, DANA, 1848, Zoophytes, p. 537; NICHOLSON, 1879, Pal. Tab. Corals, p. 292; 1881, Genus
‘ : Monticulipora, p. 97; Uuricu, 1882, Jour. Cin. Soc. Nat. Hist.,
vol. v, p. 156; 1883, idem, vol. vi, p. 265; 1890, Geol. Surv. IIl., vol. viii,
' pp. 374, 423; Tamms and JAMES. (part.) 1888, Jour. Cin. Soc. Nat. Hist.,
vol. xi, p. 29.*

Stellipora, DyzowskI, 1877. Die Chetetiden d.Ostb. Silur. form., p. 42.

Zoaria subramose or frondescent, growing erect from a basal expansion which
is attached to foreign bodies. Surface with stellate maculz, the spaces between the
rays more or less elevated and occupied by two or three short rows or clusters of
closely approximated zocecial apertures. Zocecia with rather thin walls, small
circular apertures euclosed by an elevated rim, equally distributed and partly in
contact with each other in the spaces between the macule. Interspaces depressed;
mesopores abundant, aggregated in the macule, always closed at the surface, with
gradually crowding horizontal diaphragms. Zocecial tubes with fewer diaphragms.
True acanthopores wanting, but exceedinly minute tubuli, increasing in number
with age, are to be detected in the interspaces by means of tangential sections.

‘Type: ©. florida- Ulrich.

Of this genus I am now acquainted with eight good species and three or four
varieties that group themselves around C. florida. The earliest known occurs in
the Pierce limestone of Tennessee. This is very much like the Minnesota Trenton
species next described, but as it has not yet been critically studied it may prove
quite distinct. A variety of C. florida occurs in the upper Trenton beds at Nashville,
Tennessee, and in Canada, and other varieties occur abundantly with the typical
form of the species in the lower half of the Cincinnati rocks. C. fischeri Ulrich, is a
Kentucky form from about the same horizon. In the upper part of the Hudson
river group in Ohio, Indiana, Illinois and Wisconsin, we meet with C. polystomella
Nicholson, and C. limitaris Ulrich, and with two undescribed species at Wilmington,
Illinois, This locality furnished also the types of C. parva Ulrich. These species
are all separated easily from each other by means of intelligently prepared thin

sections.

CoNSTELLARIA VARIA, 7%. Sp.
PLATE XXI. FIGS .1-7.

Zoarium consisting of one or more irregularly dividing branches arising from a
broad basal expansion. Branches usually compressed, generally from 8 to 10 mm.

wide, but varying between the extremes of 3and15mm. Macule large, irregularly

F 5 1 of James and James referred to above as unworthy of such quotation, and that its citation

— Seer ae the Bryozoa is to dignify it with an attention far beyond its deserts. But the possibility
a aes Se A Werth discover merits which I cannot may be sufficient excuse for its inclusion in the bibliography.
that other:
312 THE PALEONTOLOGY OF MINNESOTA.

(Constellaria varia.

stellate, very slightly depressed or on a level with the general plane of the surface.
The small clusters of zocecial apertures (four to ten in each) occupying the angles
between the rays may be elevated a little above the level of the macule, but as a
rule the entire surface may be said to be even. Ina few cases however the macule
themselves are higher than the spaces separating them. Zoccial apertures subcir-
cular, inclosed by a very thin rim, and varying considerably in size, though approxi-
mately equal on each fragment. Width of interspaces varying correspondingly
so that about the same number of apertures occur in a given space in all
specimens. Ten or eleven occur in 3 mm. in the intermacular spaces, while the
diameter of the apertures varies between the extremes of 0.15 and 0.25 mm. Figure 1
represents the surface of a specimen (x9) with small apertures and wide interspaces; ~
fig. 2 a small part of another (x18) having comparatively large zocecial apertures
and correspondingly narrow interspaces. The latter are always a little depressed,
and, like the macule, occupied by the shallow yet distinct mouths of angular
mesopores.

Internal characters: Figure 4 represents a portion of a tangential section where
it divides a mature zoarium immediately beneath the surface. In most sections the
walls will be thinner and probably not show the minute tubuli in them as drawn in
fig. 4. Series of sections prove that the relative width of the zocecial tubes and
interspaces depends largely upon age, the width of the zowcia decreasing with
maturity. Figure 5 is from a good vertical section, and shows that diaphragms
occur in all the tubes throughout the zoarium, in the axial region generally about
twice their diameter apart, the distance between them becoming less as the zoccial
tubes bend to the surface. In the mesopores, which are very abundant, especially
when the section passes through one of the macule, the diaphragms are at first
rather far apart, but gradually become almost crowded at the surface.

This species is nearer C. limitaris Ulrich, of the upper part of the Hudson river
group, than any other. The superficial resemblance between them is very decided,
but when we compare thin sections we find that the later species has smaller and
much more abundantly tabulated mesopores. Indeed, the diaphragms are more
numerous in both sets of tubes. All the other described species of the genus have
smaller zocecia, and most of them differ in having no diaphragms in the axial region.

None of the associated species are likely to be confused, none of them having
stellate macule.

Formation and locality.—Rather rare in the upper beds of the Galena shales near Cannon Falls,

Minnesota. It is here associated with Orthis germana W and S., Homotrypa similis Foord, and several
species of Nematopora.

Mus. Reg. No. 8044, 8130.
Nicholsonella.] BRLO2OR. 3 1 3

Genus NICHOLSONELLA, Ulrich.

Nicholsonella, ULRICH, 1890, Geol. Sur. Ill, vol. viii, pp. 374 and 421.

Zoaria consisting of irregularly intertwining flattened branches or fronds growing
from an expanded base ; or of laminar, free or parasitic, expansions only. Zoccial
tubes subcylindrical, with diaphragms only moderately numerous; apertures circular,
enclosed by a slightly elevated papillose peristome. Interspaces wide, occupied by
numerous angular mesopores more or less completely isolating the zoccia; minutely
granulose in fully matured examples. Walls of both sets of tubes thin, and in the
peripheral region traversed longitudinally by minute tubuli. With age-a perforated
calcareous deposit fills the interzocecial spaces in which the walls of the mesopores
become unrecognizable. Mesopores with thicker and generally more numerous
diaphragms than the zocecial tubes. In the axial region of transverse sections of
the erect forms the tubes are very unequal.

.Type: N. ponderosa Ulrich, Geol. Sur. IIL, vol. viii, p. 422, 1890.

This is a Lower Silurian genus with rather uncertain affinities. So far as our
knowledge goes the position of the genus in classification seems to be in a measure
intermediate between Constellaria and Leioclema. In another direction we note
considerable resemblance to Heterotrypa. The type is one of the earliest as well as
one of the most complicated and interesting of the Tvepostomata, and on the whole
appears to occupy a rather isolated position with respect to contemporaneous types
of structure. It is therefore unfortunate that the preservation of the most typical
species of the genus is almost invariably unfavorable for microscopic determination
of their internal peculiarities. Indeed, it is a noteworthy fact, that Trenton speci-
mens of Nicholsonella are but rarely as well preserved as are associated Bryozoa of
other genera.

N. ponderosa was described from the “Lower Blue” or sponge beds at Dixon,
‘Illinois, A nearly related species occurs at Beloit, Wisconsin, and in the middle
third of the Trenton shales of Minnesota. Associated with the latter is the laminar
species,, NV. laminata, about to be described. N. pulchra is a fourth species from
the “Pierce” limestone of Tennessee. NV. vaupeli* is abundant in the quarries at
Cincinnati, Ohio, as is an undescribed and closely related form occurring higher in
the series at several localities in Ohio and Indiana. Finally, N. cumulata is described
in my Illinois work from the upper beds of the Hudson river group at Wilmington,
Illinois.

—_—— .

*Heterotrypa vaupelt Ulrich, 1883, Jour. Cin. Soc. Nat. Hist., vol, vi. p. 85.
314 THE PALEONTOLOGY OF MINNESOTA.
é 7 fNicholsonella pulchra,

NIcHOLSONELLA PULCHRA, 1%. Sp.

PLATE XXI. FIGS. 8-12.

Zoarium forming a bushy mass, consisting of irregularly divided, sometimes
anastomosing flattened branches, 6 to 10 mm. thick and 8 to 20 mm. wide, Surface
with small conical or rounded menticules, subsolid at their apices, and frequently
uniting on the rounded edges of the branches to form short ridges. In some speci-
mens the monticules are very slightly developed. Zocecial apertures rounded, small,
subequal, regularly arranged, about eleven in 3 mm., separated by interspaces nearly
equalling their diameter—about 0.15 mm. Interspaces minutely papillose, generally

‘depressed midway so that a rather irregular ring of papillee surrounds each aperture.
Mesopores, though completely isolating the zocecia, are to be detected at the surface
only in young and weathered examples.

Internal characters: In vertical sections the tubes diverge with comparative
rapidity and uniformity of curvature. Their walls are thin, though not excessively
so, and exhibit that lack of sharpness which characterizes especially the Trenton
species of the genus. Young zoccial tubes arise in the axial region mainly and
expand very gradually. Diaphragms occur throughout, two or three times their
diameter apart in the axial region, and averaging nearly twice as many in a given
space in the peripheral region. In young examples it is not easy to distinguish the
mesopores from the true zoccial tubes, but the solid deposit which more or less com-
pletely fills up the outer part of the mesopores in the fully matured stages then
renders the task an easy one. This deposit is lined vertically with rows of dots, and
‘in many cases is divided up into two or more layers with light intervals between them.
The two halves of fig. 10 show, in the upper, the structure of a matured example just
beneath the surface. Here the zocecia are as usual not sharply defined and the inter-
spaces completely filled with solid tissue in which a great number of small dots
(representing the superficial papillz) are to be observed. At a deeper level in the
zoarium (see lower half of fig. 10) the large angular mesopores are open. Here even
some dots (?acanthopores) are to be made out in the walls, chiefly at the angles of
junction.

Transverse sections show that in the axial region the tubes are of all sizes and
variously angular. No dots like those seen in tangential sections are to be detected,
but one of my sections exhibits fairly conclusive evidence of an intermittent struc-

2

ture of the walls not unlike fig. 26 on plate 27.
BRYOZOA. 315

Nicholsonella laminata.]

There is,very little likelihood of confusion between the present species and any
other referred to the same genus, and thin sections will of course distinguish it at
once from species of other genera. Among the latter Monticulopora arborea, from
higher rocks, is strikingly like N. pulchra superficially.

Formation and locality—Not uncommon in the ‘‘ Pierce limestone” at Murfreesboro, Tennessee,
where it is associated with an abundance of fossils, chiefly Bryozoa.

Mus. Reg. No. 8131.

NICHOLSONELLA LAMINATA, 7. sp.

PLATE XXI, FIGS 15-19 and 21.

Zoarium laminar, several mm. thick, the under side strongly wrinkled concen-
trically. Upper surface even, but exhibiting rather indistinct macule or areas in
which the interspaces between the zocecia are wider than usual. Zocecial apertures
circular, regularly arranged, nine or ten in 3 mm., averaging 0.2 mm. in diameter
and 0.13 mm. apart. Peristome thin, very minutely papillose. Interspaces occupied
by angular mesopores forming a complete series between the zocwcia. Mouths of
mesopores closed or open. When closed the interspaces are slightly roughened by
small granules among which a few of larger size (? acanthopores) have been
detected. Internal characters as shown in figures. ;

I have taken great pains to illustrate the internal characters just as they
appeared to me under the camera lucida, and I refer the student to figs. 15, 16 and
17, rather than attempt a description. I will however admit at once that I do not
understand the purpose of the system of dots lining the walls and radiating from
the center of one of the zoccia. The latter may represent perforations in the
diaphragms.*

The surface and growth of this species remind one of species of Fistulipora with
small zocecia. The laminar form of the zoaria will, it is believed, effectually distin-
guish it from other forms of Nicholsonella. I know of no associated bryozoan with
which it might be confounded, and the mere mention of caution should deter the
student from carelessly classifying the Nicholsonella with the very different discoidal

"species of Prasopora and Mesotrypa.

Formation and locality.—Rare in the middle third of the Trenton shales at St. Paul and Min-
neapolis.

 

—

*Such pore-like “dots”
attached to this work. 8
gather facts and I shall continu
many microscopists have long 0 5
obliterated by some insidious actio
indeed necessary, to make the drawin

and other minute unexplained structures have been drawn carefully on a number of the plates
ome day perhaps we may be able to appreciate their significance. In the meantime we must
e to delineate them as faithfully as Ican. In this connection it may be well to mention wha}
bserved with dismay. Namely, that minute structures like those in question are gradually
n of the Canada balsam in which the preparations are mounted. It is therefore desirable,
gs as soon as possible after mounting the sections.
316 THE PALEONTOLOGY OF MINNESOTA.

[Nicholsonella ponderosa?

NicHOLSONELLA PonDEROSA ? Ulrich.

PLATE XXI, FIGS. 13, 14, 20 and 22.

?Nicholsonella ponderosa ULRICH, 1890. Geol. Sur. I11., vol. viii, p. 422, pl. XXXIV, figs. 5-5d.

Two specimens only of this form were found by the author at Minneapolis in the
lower third or “Stictoporella beds” of the Trenton shales. One is an irregular mass,
65 mm. long by 30 to 40 mm. in thickness, presenting the bases of several large
branches. The surface is not well preserved, but seems to have been considerably
like that of N. laminata. The interior likewise is but illy preserved, and the illustra-
tions (figs. 18 and 20) may be objected to on the ground that they are much more
distinct than the sections. The “dots” in the interspaces have, most probably
been drawn too small and too numerous. It seems that two or three should have
been united into one, giving an appearance more like fig. 10 of the same plate.
Still, enough of the internal characters are to be made out to render the generic
reference almost beyond dispute. On protected spots the surface is decidedly spinu-
lose. Here about nine zoccial apertures occur in 3 mm.

The other specimen is a fragment of a branch, about 11 mm. thick and 14
to 19 mm. wide. In the shape of the zoccia, their number in a given space, and in
the charcter of the interspaces and interior, this specimen is apparently precisely
like the first.

There is nothing decidedly opposing the placing of these specimens with N. pon-
derosa, the types of which are from the sponge-layer of the “ Lower Blue” limestone
at Dixon, Illinois. Still, better preserved material is desirable before much confi-
dence is to be placed in the identification.

Family AMPLEXOPORIDA, Ulrich.
Genus LEPTOTRYPA, Ulrich.

Zoaria varying from thin incrustations to free forms of discoidal, spiral, or
elongate conical shape; subglobose and irregularly massive species occur also.
Zoccial tubes polygonal, with thin walls just appreciably thickened in the mature
regions, and a variable number of diaphragms. Acanthopores small, more or less

“numerous, but almost invariably restricted to the angles of junction between the
zocecial tubes. Mesopores wanting.

Type: LL. minima Ulrich, of the Cincinnati group.

This genus includes forms essentially like those of Amplexopora, Ulrich, only
they arise into erect branching zoaria while the species of Leptotrypa never depart
BRYOZOA. 317
Leptotrypa hexagonalis.]

from the types of growth mentioned in the description. Numerous species of both
genera are known and several of Leptotrypa from the Trenton beds of Minnesota,
True Amplexopora, however, is first met with in the Utica.*

Leprotrypa HEXAGONALIS Ulrich. &
(Not Figured.)

Leptotrypa hexagonalis, ULRICH, 1890. Geol. Surv. Il., vol. viii, p. 455.

Original description: “Zoarium forming parasitic expansions less than 1 mm.
in thickness, spread upon Orthoceras and Hyolithes. Surface smooth. Clusters of
cell apertures of almost twice the usual size are arranged in diagonally intersecting
rows; these clusters are about 3 mm. apart, measuring from center to center. Zocecia
regularly hexagonal in shape, sometimes a little elongated, seven, measuring longi-
tudinally, almost nine, diagonally, in 2 mm.; diameter of the smaller 0.2, of the
larger 0.85 mm. Acanthopores prominent on the surface when well preserved.”

This species occurs almost invariably as a delicate lace-like expansion upon
Hyolithes baconi Whitfield. This fact, together with the markedly hexagonal shape
of the zocecial apertures, renders it an easily recognized species. :

Formation and locality—Rather rare in the limestone at Minneapolis, Minnesota. The types are
from equivalent beds (‘‘Lower Blue”) at Mineral Point, Wisconsin, and Calhoun county, Illinois. Other
localities are Janesville and Beloit, Wisconsin.

Mus. Reg. Nos. 7551, 7557, 7595.

LEPTOTRYPA INFORMIS, n. Sp.

PLATE XXVII, FIGS. 22 and 23.

Zoarium forming parasitic patches or lump-like growths upon foreign bodies,
varying considerably in size and from 1 to 5 mm. in thickness. At other times
apparently free, with a wrinkled epitheca beneath. Surface without monticules,
nor are the clusters of large cells very conspicuous except in a few cases where the
zocecia forming them are separated by a limited number of small cells. Zoccial
apertures polygonal, thirteen or fourteen of the average size in 3mm. Walls very
thin, in vertical sections sometimes appearing as though made up of alternating
horizontal bands of light and dark shades. Acanthopores more or less prominent
at the surface, varying some in size, restricted to the angles of junction, one-half of
which are occupied by them. Diaphragms complete, on the whole rather remote
and irregularly distributed, the intervals between them varying from one to four

times their diameter.

t both Mr. A. H. Foord and myself, but a re-examination
ecies have been placed under Amplexopora by
has oe ne that the species in question are more likely aberrant types of Batostoma, where I would now place

them.
318 THE PALEONTOLOGY OF MINNESOTA.

{Leptotrypa acervulosa.

In many respects like L. semipilaris Ulrich, of the Cincinnati rocks, the most
striking difference appearing in the number of the diaphragms, these being almost
totally absent in that species. An undescribed species, differing chiefly in having
much smaller and fewer acanthopores, occurs in the Galena shales.

‘Formation and locality.—In the lower and perhaps also in the middle third of the Trenton shales
at Minneapolis and St. Paul.

Mus. Reg. No. 6024.

LEPTOTRYPA ACERVULOSA, %. Sp.

PLATE XXVII, FIGS. 24 and 25.

Zoarium occurring as small, irregular or subglobular masses, generally between
15 and 20 mm. in diameter and somewhat less in hight. Surface approximately
even, but clusters of cells are conspicuously larger than the average, and in one
case these are elevated into low monticlues. Zocecia angular, thin-walled, thirteen
to fifteen, commonly fourteen of the usual size in 8 mm.; average diameter of aper-
tures in the .spaces between the clusters about 0.21 mm., of the largest in the
clusters 0.35 to 0.4 mm. New tubes are interpolated in a great measure at cor-
responding levels through the zoarium, so that immediately above and beneath such
a level there may be considerable difference in the average size of the tubes. Dia-
phragms from one to one and a half times their length apart except in the mature
regions where they are separated by intervals about half as long. Acanthopores
very small, in the angles, developed at intervals only, no trace of them being visible
in some of the transverse sections. At the surface they are but rarely to be distin-
guished, In a single example, however, many of the angles of junction are prom;
inent and the walls between them crowned with a closely arranged ‘row of minute
papille. |

L, acervulosa agrees in most respects very closely with an undescribed species
occurring at Clarksville, Ohio, in the upper beds of the Hudson river group. Smooth
examples of L. (Monotrypq) irregularis Ulrich, also from Ohio,tire likewise simulated,
but that species is distinguished by having tubes practically without diaphragms.
Two other species from the Cincinnati exposures, L. filiosa d’Orb., sp. and L, petasi-
formis Nich., sp., are probably the nearest among described species. The first grows
in large masses and has well developed monticules, while the second forms hat-
shaped or hemispheric zoaria like Prasopora simulatriz,

Formation and locality.—Not uncommon in the Galena shales at’ Decorah, Iowa. A single speci-

men from the same horizon in Goodhue county, Minnesota. Also in the shaly part of the Trenton at
Burgin and Frankfort, Kentucky.

Mus, Reg. No. 8060.
: BRYOZOA. 319
eptotrypa claviformis.]

LEPTOTRYPA CLAVIFORMIS, n. Sp.

PLATE XXVII, FIGS, 20 and 21,

Zoarium growing around and beyond one or more segments of Arthroclema and
Helopora into simple club-shaped forms varying from the smallest figured to one
that is 23 mm. long and 1.5 to 2.5mm. in diameter. Some of the specimens have one
or two short lateral branches, in which cases the supporting body was a twig of
Arthroclema with lateral segments in place. Zocecial tubes growing about the axial
body very much as in ordinary ramose forms they grow about an imaginary center;
diaphragms abundant except in the outer or direct portion; walls thin. Zoccial
apertures subangular, nearly uniform in size, there being no appreciable clusters of
large cells; without apparent arrangement, about fourteen in 3mm. What may be
mesopores, but more likely are merely young zocecia, are scattered among the
ordinary tubes. At intervals, however, they seem to be more numerous than usual.
Many, perhaps the majority, of the angles of junction are thickened and occupied by
projecting acanthopores.

In a general way, this species may be said to fall under Leptotrypa, but I
am more than inclined to doubt that it belongs there. The interior of the speci-
mens sectioned is but illy preserved, the finer details of structure being quite
obscure. Some of the specimens remind of Petigopora, Ulrich, and it is here that
better sections will probably cause us to refer them.

Formation and locality—Rather common in the middle and upper thirds of the Trenton shales
at St. Paul and Minneapolis.

Mus. Reg. No. 8182.

Family CERAMOPORIDA, Ulrich.
Genus SPATIOPORA, Ulrich.

Spatiopora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 155, and 1883, vol. vi, p. 166; Foorp,
1883, Contri. Micro-Pal. Cambro-Sil. Rocks, Can., p. 20; ULRICH,
‘ 1890, Geol. Surv. Ill., vol. viii, p. 381.

Zoaria forming thin parasitic crusts upon foreign bodies, the shells of Orthoceras
being the most favored. Surface even or with monticules. Zocecia short, with
direct and more or less irregularly shaped apertures. Lunarium scarcely perceptible
even in thin sections. Mesopores very few, usually absent, when present occurring
chiefly as “macule.” Interspaces often with large blunt spines (?acanthopores).
Walls of zocecia moderately thin, with the characteristic structure pertaining to the
family.

Type: 8. aspera Ulrich.
320 THE PALEONTOLOGY OF MINNESOTA.

[Spatiopora labeculosa.

Two Trenton species, S. areolata Foord, and S. labeculosa Ulrich, are referred to
the genus with doubt.* The type, together with four or five other species, is found
in the Cincinnati or Utica and Hudson river groups, above which the genus is not
known to pass.

SPATIOPORA LABEOCULOSA, 7. Sp.

PLATE XXVIII, FIGS. J and 2.

Zoarium forming large and very thin expansions generally upon Orthoceras or
Endoceras. Surface even, but conforming with the irregularities of the body grown
upon, At intervals of ‘4 or 5 mm., measuring from center to center, there are
clusters of cells decidedly larger than the average. These large apertures—they
vary from 0.25 to 0.50 mm, in diameter—are arranged in each case about a sub-
stellate or irregular, apparently solid, spot, which on closer examination proves to
consist of closed mesopores. The extent of these spots varies greatly, some being
almost 2 mm. wide, while in others the center is scarcely more than 0.5 mm. wide.
Zocecial apertures subangular, usually a little oblong, with the margin on one side
generally a little higher and more rounded than on the other. The last is true more
particularly of the large cells which are not infrequently decidedly oblique and
directed away from the center of the macule. In very young examples all of the
apertures may be quite as oblique as in some species of Ceramoporella, but the
lunarium is ever an inconspicuous feature. Many of the large cells again may
preserve peculiar convex closures, Of the smaller or average zoccia eleven to
thirteen occur in 3mm. Mesopores varying in number and distribution, but some-
thing like the following rule seems to prevail. When the macule are large the
mesoposes are few and of small size elsewhere (see figs. 1 and 2); when small they are
comparatively more abundant in the inter-macular spaces.

Internal characters: Figure 2 is a faithful copy of a portion of a tangential
section prepared from a specimen (fig. 1 is an enlargement of its surface) having
large macule. It will be noticed that the side of the zocecia nearest the macula is
nearly always less angular than the opposite side. This fact is good evidence of the
possession of an incipient or undeveloped lunarium. The minute structure of the
walls, which is not the same as in Leptotrypa, is likewise indicative of ceramoporoid
affinities. In vertical sections the prostrate part of the tubes is rather short, and
the erect part, forming an angle of about 80° with the line of the surface, perhaps

*Since this report was placed in the hands of the printer. two specimens of a typical species of this genus were collected
by the author in the upper part of the middle third of the Trenton shales at Chatfield, Minn. The specific characters
of these specimens, which grew over the shells of a small Orthoceras, are very similar to those of S. maculosa and S. lineata
Ulrich, of the Oincjpnati rocks, As a provisional designation for the form I would propose the name S. maculosa, var.
incepta.
BRYOZOA. 321

Spatiopora iowensis.]

never exceeds 1 mm. Diaphragms are wanting in most of the tubes, but here and
there the sections pass through one or several adjoining tubes having one diaphragm

. about midway up and sometimes another at the month.

«

This is an interesting and easily recognized species. Of associated parasitic
forms only two need be compared; one, Stromatotrypa ovalis of this work, has oval
and much larger zocecia; the other is a rare and as yet undetermined form with
circular and smaller zocecia, numerous mesopores, and more uneven zoarium. S.
labeculosa differs from both in the greater size and distinctness of its macule, and in
the slight obliquity of its zocecial apertures. The macule will distinguish the species
at once from all the other species of the genus.

Formation and locality.—In the middle third of the Trenton shales at Minneapolis and St. Paul.
Mus, Reg. No. 5026.

SPATIOPORA IOWENSIS, ”. Sp.

(Not figured.)

Zoarium spread as an exceedingly thin crust over the cones of Orthoceras sociale
Hall. Monticules wanting, but unusually distinct clusters of large cells are dis-
tributed over the surface at intervals of about 5 mm., measuring from center to
center. Zocecia larger than in other species of the genus, their walls thin, the
apertures nearly or quite direct, angular, often of hexagonal or rhombic shapes, with
three of those in the clusters in 2 mm. and an average of nine of those in the spaces
between the clusters in 3mm. Mesopores wanting except in the clusters mentioned
where a few may be wedged in among the large cells. Many of the angles of junc-
tion between the apertures are raised into sometimes small, at other times large,
acanthopore-like prominences.

In the dark shales at Graf, Iowa, this bryozoan is preserved as a thin gladiolus
leaf-like film, the Orthoceras grown upon being compressed to such a degree that its
original presence may not be suspected.

This species is in every respect a true Spatiopora. The affinities are nearer
S. maculosa Ulrich, of the Cincinnati rocks, than to any of the others, and it is with
that species that I first thought to place it. On comparison however S. iowensis
proved to have larger zocecia, with eight to ten where the Ohio species has eleven or

twelve.

Formation and locality. Maquoketa shales of the Hudson River group at Graf, Iowa.

Mus. Reg. Nos. 7586, 7587.
—el
322 THE PALEONTOLOGY OF MINNESOTA.

(Crepipora.

Genus CREPIPORA, Ulrich.

Crepipora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 157; 1890, Geol. Surv. II1., vol. viii,
pp. 380, 469.

Zoaria incrusting, massive, or hemispherical; in one case forming regular hollow
branches. Surface, especially in the first and last styles of growth, exhibiting at
regular intervals macule of mesopores, appearing as minutely porous or subsolid
elevations or depressions. In the massive forms these macule, to which the meso-
pores are usually restricted, are very small. Zocecial tubes erect, their apertures
very slightly oblique and varying from rhomboidal to subpyriform in shape. Luna-
rium small and easily overlooked except in well preserved examples; best shown in
tangential sections. Thin diaphragms are developed in moderate numbers.

Type: C. simulans Ulrich.

Eleven or twelve species, several as yet undescribed, are known to me having
the characters ascribed to this genus. Three of these are Trenton, the rest, save an
Upper Silurian species from Gotland, are Utica or Hudson River group forms.

Crepipora differs from Ceramporella in having much fewer mesopores (typically
none) in the inter-macular spaces, longer tubes, and less oblique apertures. C. epi-
dermata Ulrich, from the Hudson River group of Illinois, is closely related to the new
genus Bythotrypa, and ought perhaps to be referred to that genus, but it has seemed
the wiser course to leave the species as originally described until special investiga-
tions into the inter-relations of the Ceramoporide can be taken up.

CREPIPORA SUBEQUATA, 7. Sp.

PLATE XXVIII, FIGS. 26-28. “

Zoarium a small laminar or incrusting expansion, 1 to 3 mm. thick. Zocecial
apertures approximately direct, angular, often quadrate or pentagonal, of nearly
uniform sizes on all parts of the surface, no distinguishable clusters of cells larger
than the average having been developed; ten in 3 mm. Lunarium very slightly
developed, the zocecial apertures and walls appearing much more like those of
species of Monotrypa than of a ceramoporoid. Tangential sections, however, (see figs.
26 and 27) afford more or less clear evidence of its presence, but it is rare to find
more than one of the ends of the lunarium projecting inward from the wall. Many
of the angles of junction are thickened and include an acanthopore-like structure.
BRYOZOA. 323

Crepipora spatiosa. ]

Mesopores very few. In vertical sections the walls are thin, with faint transverse
lineation, and somewhat irregular. Diaphragms occur sparingly and at unequal
intervals in the zocecial tubes, but in the mesopores which, being few, are not often
seen, they are numerous. :

The absence of clusters of large cells and the greater average size of the
ordinary zocecia will distinguish this peculiar species from associated Bryozoa
having a similar mode of growth.

Formation and locality.—Rare in the upper third of the Trenton shales at St. Paul, Minnesota.

CREPIPORA SPATIOSA, ”. Sp.

(Not figured.)

This name is proposed for a massive or heavy lamellate form that occurs in the
Bryozoa layers at the top of the Trenton near Harrodsburg and Frankfort, Ken-
tucky. It is closely related to C. hemispherica Ulrich (upper beds of Hudson River
group in Illinois), on the one side, and C. perampla on the other. From the first it
differs in the greater size and different shape of its zoarium, in haying thinner walls
and fewer diaphragms, and less distinct lunarium. The second has*larger zocecia
and even less developed lunarium, but in other respects is very similar to the Ken-
tucky species.

Specimens of this species may attain a diameter of 300 mm. with a thickness of
from 50 to 100 mm. Of the ordinary zowcia twelve occur in 5 mm. Diaphragms

0.4 to 1.0 mm. apart.

CREPIPORA PERAMPLA, #. Sp.

PLATE XXVIII, FIGS. 29-32.

Three specimens have been seen of this. One, about 70 mm. in diameter and
33 high, is hemispheric, with the base concave and the margin flaring slightly. The
others are larger (about 95 mm. in diameter) and, though worn, the basal part of
the zoarium seems to have been convex instead of concave. Zocecia large, with very
thin walls, generally of angular shapes, the pentagonal and hexagonal more common
than the subrhomboidal; those of the average size about 0.5 mm. in diameter, with
nine or tenin5 mm. At intervals of 5 or 6 mm. clusters of tubes of more or less
decidedly larger size than the ordinary are to be observed. Some of these may

attain a width of 0.9 mm., but as a rule their size varies between 0.6 and 0.8 mm.

Mesopores very few.
324 THE PALEONTOLOGY OF MINNESOTA.
[Bythotrypa’

The appearance of thin sections is shown in the figures on plate XXVIII. In
figs. 30 and 81 the presence of the lunarium is shown in an unmistakable manner,
but fig. 32 is more like the usual appearance. Indeed, the lunarium is often so
difficult to distinguish in transverse sections, that it is in order to caution the stu-
dent against confusing the species with Monotrypa. In vertical sections the walls
are often minutely crenulated, and in most cases exhibit the transverse lineation so
common among the ceramoporoids. Exceedingly thin diaphragms occur in all the
tubes at intervals varying from one to two tube-diameters. __

The great size of the zocecial tubes separates this species from all the other
forms of Crepipora known. In this respect the species is approached by but one other
paleozoic bryozoan, the Monotrypa magna of the present work, and both are believed
to occur in nearly the same geological horizon. These two forms also present some
points of resemblance in vertical sections, but so far as I can see there is really no
relationship between them. In the Monotrypa the zocecia are much more regularly
angular, their walls without the transverse lineation and more coarsely wavy, while
a lunarium is of course never present. The C. hemispherica Ulrich, which seems to
occur in the shales of the Hudson River group at Granger and near Spring Valley,

differs chiefly in the smaller size of the zocecial tubes.

Formation and locality.—Trenton limestone at Chatfield and two miles northeast of Spring Valley,
Minnesota.

Mus. Reg. Nos. 151, 170, 211.

Genus BYTHOTRYPA, n. gen.

Zoaria massive or lamellate. Zocecia forming long continuous tubes, intersected
by thin diaphragms, their walls minutely crenulate and with the structure charac-
terizing the ceramoporoids. Lunarium well defined, large, projecting above the rest
of the aperture margin. Mesopores numerous, open at the surface, interiorly form-
ing a species of vesicular tissue unusually loose and irregular in construction.

Type: Fistulipora laxata Ulrich.

Largely increased collections of the type of this genus have convinced me that
the species really belongs to the Ceramoporide. As none of the established genera
of that family would include it, a new generic division became necessary. Bythotrypa
is probably, as I regarded it at first, a type of structure that culminated in true
Fistuliporide, but the lines along which the development progressed we are as yet
unable to define. Still, it is more than possible that we have here merely a fore-
shadowing of that family—in other words, a premature evolution of the fistuliporoid
Bythotrypa laxata.] BRYOZOA. 325

type—that became extinct or was reabsorbed into the parent stock, failing to estab-
lish a permanent line of development. In that case Crepipora? epidermata Ulrich,
from the Hudson River rocks of Illinois, would seem to be the earliest known point
in the direct line to Fistulipora.

Byrnorrypa Laxata Ulrich.
PLATE XXVIII, FIGS. 21-25,

Fistulipora? lawata ULRICH, 1889, Contri. Micro-Pal. Cambro-Sil. Rocks, Can., pt. ii, p. 37.

Zoarium irregularly massive, usually beginning its growth upon some foreign
body, the exposed under side strongly wrinkled and covered with an epithecal mem-
brane. Specimens vary greatly in size, the smallest seen being about 12 mm. in
diameter and 5 mm. or less high, while the Jargest is an oval mass 150 mm. long,
120 mm: wide, and about 70 mm. high. In the lower third of the Trenton shales
they are all small, none observed exceeding 50 mm. in diameter. In the middle
and upper thirds specimens between 75 and 100 mm. wide are not rare, but masses
exceeding that size have been met with only in the upper part of the Galena shales.

Zocecial apertures subovate, nearly equal, direct or a little oblique, the lunarium
broad, sharply elevated, sometimes seeming to arch slightly over the aperture; their
arrangement appearing more irregular than it is, with nine or ten in 5mm. Meso-
pores abundant, varying greatly in size, a few quite as large as the zoccia from
which they are distinguished by their more angular and irregular form and in being
without a lunarium. Mesopores forming larger or smaller clusters at irregular
intervals from which the zocecial apertures are turned in a radial manner. These
clusters are most inconspicuous—even difficult to make out under the glass—except
under certain conditions of weathering when they stand out as subsolid spots.
Under ordinary circumstances the whole surface seems to be occupied uniformly
by an irregular network of cells.

Internal characters: In transverse sections the appearance, aside from an unusual
irregularity and looseness of arrangement, is much as in species of Fistulipora. The
zocecia are irregularly pyriform or ovate in cross section, and have thin walls. The
lunarium, though often not a very marked feature, is still always determinable by
the more regularly curved semi-circular form of the lunarial side of the circumfer-
ence of the zocecium, the opposite side being, if not angular, at any rate always
drawn to a circle of greater diameter than the lunarial side. Occasionally one or
both ends of the lunarium may project into the zocecial cavity (see fig. 25). Not

infrequently also the lunarial side is thickened by a light-colored deposit upon the
326 THE PALEONTOLOGY OF MINNESOTA.
(Anolotichia.

outer side in which very fine transverse lines may be noticed. Dimensions of
zocecium of average size, about 0.3 by 0.4 mm. Interstitial cells varying greatly in
size and distribution, some being very small, others as large and even larger than
the zoecia. They form generally but a single series between the zocecia, yet it
is not uncommon to notice a double row fora short distance. An obscure radial
arrangement, with the zoccia in contact lengthwise, is noticeable about certain
points, 6 mm. or more apart, where the interstitial cells are more numerous than
elsewhere, without, however, at any time being in sufficient numbers to justify
being called “ macule.”

Vertical sections are even more characteristic, since in these the loose construc-
tion mentioned is very striking. The zocecia appear as long irregular tubes crossed
at variable intervals by exceedingly delicate horizontal diaphragms. The average
distance between the diaphragms depends somewhat upon the horizon from which
the specimen was collected. In zoaria from the lower and middle thirds of the
Trenton shales, the average is between 0.5 and 0.9 mm., but in those from thé Galena
shales it is between 0.8 and 1.2mm. The interstitial cells assume all sorts of shapes,
but are always extremely high. A tendency to arrange themselves in vertical series
is usually manifest, but they cannot be said to form tabulated tubes, their walls
being on the whole quite irregular and the end partitions more or less oblique and
in many cases overlapping. All the walls have that peculiar granular structure
noticed, in paleozoic Bryozoa, only among the Ceramoporide and Fistuliporide.

Both the external and internal characters of this species are so distinctive that
there is little or no danger of confusing it with associate massive forms.

Formation and locality.—Not rare in the three divisions of the Trenton shales at Minneapolis, St.
Paul and Cannon Falls. It reappears, larger than ever, in the upper part of the Galena shales at several
localities in Goodhue county, Minnesota, and at Decorah, Iowa. The original Manitoba type of the
species I now believe to have come froin strata equivalent to the last. It was collected at St. Andrews.

Mus. Reg. Nos. 5963, 7602.

Genus ANOLOTICHIA, Ulrich.

Anolotichia, Ulrich, 1890. Geol. Sur. Ill., vol. viii, pp. 381 and 473.

Zoaria large, irregularly ramose or digitate. Zocecia comparatively large, form-
ing long prismatic tubes, intersected by complete diaphragms more or less remotely
situated. Walls thin, appearing transversely lineate in vertical sections. Apertures
angular or subovate, direct, with a distinctly elevated lunarium. Thin sections show
the lunarium to be traversed lengthwise by from two to seven minute, closely tabu-
lated tubes. Mesopores very few in A. impolita, but moderately abundant, rather
equally distributed among the zocecia, and of irregular form, in the type species.
BRYOZOA. 327
Anolotichia impolita.]

Type: A. ponderosa Ulrich, Hudson River group, Wilmington, Illinois.

Only two species, the type and the one next described, are as yet known of this
remarkable genus. Aside from the lunarial tubuli, which constitute the principal
distinctive character, the genus corresponds rather closely on the one hand, through
A. impolita, with Crepipora, and fully as well on the other, through A. ponderosa
with Chiloporella. In the absence of any positive knowledge concerning the functions
and classificatory value of the lunarial tubuli, the relationships noted must provis-

ionally determine the systematic position of Anolotichia as intermediate between
those genera. ,

AnoLoricHia impotita Ulrich.
PLATE XXVIII, FIGS. 15-20,

Crepipora impolita ULRIcH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 77.

Zoarium large, bushy, consisting of abundantly and irregularly divided solid
branches, the latter varying from 5 to over 20 mm. in diameter. At the base the
branches may coalesce, and here they are always stronger than at their termina-
tions. Rarely the zoarium is not branched but occurs as an irregular mass with
lobe-like excrescences. Zocecia large, with moderately thin walls, direct, hexagonal
or subrhomboidal apertures. The latter are subequal (there being no distinguish-
able clusters of large ones), are arranged in rather regular series with eleven in 5mm,
Lunarium well developed, appearing as a small crescentic elevation usually in one
of the angles. Mesopores few, sometimes appearing to be absent entirely; occa-
sionally forming small clusters of from two to six.

Internal characters: In tangential sections the walls of contiguous zocecia
appear to be thoroughly amalgamated; the lunarium is represented by two or three
small lucid spots (lunarial tubuli) on one side of the tube, the end ones projecting
slightly into its cavity. In vertical sections the tubes are scarcely to be called
vertical even in the axial region, curving outward with a uniform curve from the
beginning. Their walls are composed of rapidly alternating dark and lighter shades

-of schlerenchyma, so that they appear more or less distinctly lineate transversely.
The cause of these lines, which are closest in the peripheral part of the zoarium, is
unknown, unless the light ones, which are of uniform width and, especially in the
axial region, narrower than the dark bands, represent rows of perforations. Exceed-
ingly delicate diaphragms, their diameter or more apart, occur chiefly in the outer
and middle parts of the tubes. The axial portion of transverse sections is very nearly
like tangential, the only difference being that the walls are a little thinner and.

small tubes comparatively more abundant.
328 THE PALEONTOLOGY OF MINNESOTA.

[Ceramoporella.

The much smaller number of mesopores is the most obvious external difference
between the present species and A. ponderosa Ulrich. The lunarial tubuli also are
about twice as numerous in that species. Of Minnesota species, I know of only one
that is likely to be confounded. This is the Batostoma ‘magnopora, a rare species of
the middle third of the shales (Rhinidictya beds), having, if not always monticules,
at least conspicuous clusters of large cells. The absence of such clusters in the
Anolotichia renders the separation of the two forms comparatively easy after all.

Formation and locality.—This is a very- abundant and highly characteristic fossil of the lower
third of the Trenton shales at St. Paul, Minneapolis, Cannon Falls, Chatfield, Lanesboro and Fountain.

Mus. Reg. Nos. 5958, 5962, 7660.

Genus CERAMOPORELLA, Ulrich.

Ceramoporella, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 156; Geol. Surv. Ill., vol. viii,
pp. 380, 464.

Zoaria incrusting, often becoming massive by the superposition of numerous
thin layers. Zocecial tubes short, their walls thin. Apertures more or less oblique,
hooded, commonly of oval shape. The hoods are directed away from the centers of
small macule marking the surface at rythmical intervals. Mesopores abundant,
often completely isolating the zocecia, their apertures usually open, sometimes closed
by a thin membrane. Diaphragms only rarely present.

Type: C. distincta Ulrich, Cincinnati group, Ohio.

This genus embraces all the parasitic Lower Silurian ceramoporoids. The
species, with few exceptions, are all closely related, and some of them seem also
to have an unusually extended vertical range. Thus the first of the following
Minnesota species, which occurs here in the lowest member of the shales, is so
much like the Cincinnati types of the genus that I cannot distinguish them. C.
inclusa is a well marked species, and unknown above the upper third of the Trenton
shales, but the Galena shales species, C. interporosa, n. sp., is likewise a common
form throughout the lower 300 feet of the rocks at Cincinnati, Ohio.

CERAMOPORELLA DISsTINCTA Ulrich.
PLATE XXVIII, FIG. 13.
Ceramoporella distincta ULRICH, 1890. Geol. Surv. Ill., vol. viii, p. 464.
Zoarium forming thin parasitic patches upon other Bryozoa, the Minnesota speci-

mens seen consisting of but a single layer less than 0.7 mm. thick. Zocecia small,
radially arranged about certain small macule, nine to eleven, measuring obliquely,
BRYOZOA. 329

Ceramoporella inclusa.]

in3mm. Apertures very oblique, with an overhanging hood, highest. posteriorly.
Mesopores numerous, small, usually forming a single linear series between the sides
of the zoccia.

This species is much rarer than the associated C. inclusa from which it: is at
once distinguished by its smaller and differently shaped zocecial apertures. In C.
interporosa the apertures are larger and more direct.

Formation and locality—Lower third of the Trenton shales at Minneapolis and St. Paul. It is
met with next in the Cincinnati rocks, being an abundant species at that locality.

CERAMOPORELLA INCLUSA, 7. Sp.

PLATE XXVIII, FIGS, 8-11.

Zoarium forming thin crusts over foreign bodies, not observed to consist of
more than a single layer, less than 1 mm. thick, generally 20 mm. or more in
diameter. The customary macule, about which the zoccial apertures are arranged
in a radial manner, are represented, but less distinctly than usual. Nor is the
radial disposition of the apertures as marked a feature as usual. Indeed, it is
common to find, as-shown in figure 8, all of them turned toward the nearest
margin of the zoarium. Zocecial apertures oval, occupying, with three mesopores,
the bottom of subtriangular or rhomboidal, obliquely depressed spaces. One of
these mesopore-pits is in front, the second and third on the sides of the true aperture,
the posterior side of the latter being formed by the strongly elevated lunarium
which in this species is an unusually prominent feature. Arrangement of apertures
only moderately regular, eight or nine in 3mm.

Numerous deviations from the above described normal characters of this species
are shown in the abundant material before me. Most of them are due to imperfect
preservation and irregularities of growth, and all of them are of a nature that can
be interpreted successfully only by extended study of specimens.

The inclusion of each zocecial aperture and mesopores in a subtriangular en-
closed space, and the strong development of the lunarium are distinctive for the
species. These features are less constant in what I presume to be a mutation of the
species (toward the Cincinnati group C. ohioensis Nicholson) occurring in the upper

third of the Trenton shales.

Formation and locality—Common in the lower and middle thirds of the Trenton shales at
Minneapolis, St. Paul, and various localities in Goodhue and Fillmore counties. Rare and less typical in
the upper third of the shales at St. Paul and Cannon Falls.

Mus. Reg. Nos. 7624, 7656, 7661, 7662, 8380.
330 THE PALEONTOLOGY OF MINNESOTA.

(Ceramoporella interporosa.

CERAMOPORELLA INTERPOROSA, ”, Sp.

PLATE, XXVIII, FIG. 12.

All the Minnesota examples seen are thin crusts upon foreign bodies, but in the
Cincinnati rocks the species often forms large masses by superposition of numerous
layers. The zocecial apertures are larger, more direct, and comparatively wider than
in C. distincta Ulrich, with an average of nine in 8 mm. Fig. 12 represents the
usual appearance of the surface. Sometimes the lunarium is better distinguished
from the rest of the posterior hood than shown in the figure. The mesopores are
always numerous and generally more equally distributed around the zocecia than in

other species of the genus.

Formation and locality.—In Minnesota the species has been noticed only in the Galena shales of
Goodhue county. At Cincinnati, Ohio, the same species apparently is not uncommon in the lower 300
feet of strata. ‘

Mus. Reg. No. 7647.

Genus DIAMESOPORA, Hall.

Diamesopera, HALL, 1852, Pal. N. Y., vol. ii, p. 158 (not defined); Pal. N. Y., vol. vi, p. xv, 1887:
Uxricu, 1890, Geol. Surv. Tl., vol. viii, pp, 380, 467.
Ceeloclema, ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v (not defined).

Zoaria ramose, branches hollow, lined internally with a striated epitheca. In
other respects very much like Ceramoporella and Ceramophylla.

This name stands for au easily recognized division of the Ceramoporide. The
genus may be more convenient than natural, yet I must confess that the evidence
so far gathered points rather to an opposite conclusion. The species next described
is the earliest known. Several occur in the Cincinnati rocks, but it is not till we
come to the Niagara that the genus has its greatest development, both in the way
of species and individuals.

DIAMESOPORA TRENTONENSIS, ”. Sp.

PLATE XXVIII, FIG. 14.

Zoarium consisting of small hollow branches varying from 1.5 to 3.5 mm. in
diameter; thickness of zoarium 0.4 to 0.8 mm.; axial tube varying in diameter, the
epithecal lining not observed. Small macule sometimes present. Zocecial aper-
tures oval, about their diameters apart, arranged sometimes regularly in diagonally
intersecting rows, at other times as shown in fig. 14; averaging nine in 3 mm.
When regularly arranged they are set into obliquely depressed subrhomboidal areas,
eoeaaGia BRYOZOA. 331

reminding of Ceramoporella inclusa (see pl. XXVIII, figs. 8-11). The lunarium, how-
ever, is never prominent as in that species, nor is the posterior border of the aperture
elevated as much as is usual among Lower Silurian ceramoporoids. Mesopores two
or three to each zocecium, placed indiscriminately among the larger apertures or
one on each side and a third in front of the zocecial orifice.

This species is closely related to both D. vaupeli and communis Ulrich, of the
Cincinnati group of Ohio, but it is clearly not identical with either. In the first
place the Trenton form is always smaller, so that they may be distinguished at once
by the matter of size alone. Then the lunarial rim is not so high and the arrange-
ment of the mesopores and other superficial parts generally a little different.

Formation and locality.—In the upper third of the Trenton shales, and in the Galena shales at
St. Paul and Cannon Falls. Also in the Trenton limestone at Trenton Falls, New York, and Ottawa,
Canada.

Genus CERAMOPHYLLA, n. gen.

Zoaria erect, bifoliate, the two layers grown together back to back; in other
respects like Ceramoporella and Diamesopora.

Type: C. frondosa, n. sp.

The leaf-like zoarium of the only species of this genus known, is in many
respects very much like that of Rhinopora, Hall. Still they are very different struc-
turally, and I am satisfied that the relationship between them must be quite remote.
On the other hand, Ceramophylla may be justly called a bifoliate Ceramoporella, just
as Diamesopora would be a ramose one.

CERAMOPHYLLA FRONDOSA, 2. Sp.

PLATE XXVIII, FIGS. 3-7,

Zoarium arising from a small basal expansion into erect, leaf-like, undulating
fronds, celluliferous on both sides; thickness varying from 0.5 to 2.0 mm., but aver-
aging less than 1 mm.; largest frond seen about 40 mm. high; margins rounded,
exposing the mesial lamine. At intervals of about 3 mm. the surface exhibits more
or less conspicuous, substellate macule of mesopores. Zocecial apertures ovate,
oblique, the posterior margin well elevated, arranged more or less regularly in
transverse and diagonally intersecting series, with about eight in 3 mm. Mesopores
one, two, or three to each zocecium, variously arranged, often irregularly distrib-
uted. In the most regular and normally developed examples the zocecial apertures
332 THE PALEONTOLOGY OF MINNESOTA.

(Ceramophylla frondosa.

ate ovate or pyriform and narrowest and highest behind, while in front of the
depressed anterior side of each there is either one large triangular mesopore or
three small ones, the whole in each case being contained in an obliquely concave
‘rhomboidal space.

Of internal characters it is sufficient to say that diaphragms are wanting, the
primitive or prostrate part of the tubes thin-walled and in most cases longer than
the erect portion. In the latter the interspaces are very thick and, in vertical sec-
tions, crossed obliquely by dark lines.

Of associated bifoliate Bryozoa only Eurydictya multipora grows into broad
fronds. But the merest tyro in the science must find the task of identifying the
Ceramophylla an easy one.

Formation and locality.—Over one hundred examples were collected at St. Paul in the upper third
(Phylloporina beds) of the Trenton shales. It is rarely met with in the same beds in Goodhue county.

Mus. Reg. No. 8381.

Nore:—In the preceding report on the Bryozoa the author has adopted a merely provisional
nomenclature of the divisons or beds into which the Trenton formation of Minnesota is divisible, partly
upon lithological, but more especially upon paleontological grounds. This is in accordance with an
agreement among the several authors at work on the paleontology of the Lower Silurian rocks of
Minnesota. We believed, namely, that it was best to defer the adoption of permanent names for the
faunal zones till the study of all the classes had been completed. The subject, therefore, will be found
treated in a comprehensive manner in the introductory chapter to the volume. In that chapter a full
list of the Trenton and Hudson River fossils found in the state is given, and each is referred to its
proper horizon in the series.
 

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PLATE I.

PAGE.

Fig. 1 to 5. VINELLA REPENS Ulrich... .....0. cece ces ece cence eee eee ee rene ence na seea se seneeeneeens

1. Two colonies attached to the inner side of a ventral valve of Strophomena septata W.
and S.; natural size. .

2. Portion of one of the colonies magnified x18. The pores are absent, probably not having
been preserved. ;

3. Another portion of same zoarium X18, showing a nucleus with five divisions of the
tubular stolon radiating from it. This portion of the specimen also preserves some
of the pores marking the points where the zocecia were attached.

4, Another specimen attached to a fragment of shell; natural size. :

5. Small portion of same, X18, with three tubes lying parallel with each other. The longi-
tudinal lines are stronger ‘than usual.

Upper third of the Trenton shales at St. Paul.*

Figs. 6 and 7. STOMATOPORA TENUISSIMA Ulrich. ......ceccsceeeevencceseeeeeeernteeeee tee ceneee
6. Portion of zoarium, <9, showing its slender zocecia and mode of growth, Utica Horizon,
Cincinnati group, Cincinnati, O.
7. Several zooscia of same X25, to show their apertures and form more clearly.

Figs. 8 to 12. SToMATOPORA PROUTANA S. A. Miller.........ccccececccecceeeeceeeee eee eeeeeeeneees
8and 9. Zoarium natural size and portion x9.
10. Several zocecia of same, *25. 1
11. Several zocecia of same colony, a little more slender than usual, X25.
12. Several cells of a-form of this species in which they are unusually large, X25. (Survey
Museum. Reg. No. 5926.)
Middle third of the Trenton shales at Minneapolis and St. Paul.

Figs. 13 to 21, STOMATOPORA INFLATA Hall..... .-.cccceccecesec ee eeeeceeeee ee ceeeeteeneeneeeennes

13 and 14. A colony attached to inner side of a fragment of shell, natural size, and a portion
of same x9.

15 and 16. Another colony, natural size and a portion x9,

17. Three zowcia of same, X18, one of them preserving traces of the minute pores that pierce °

the wall.

18. Vertical section of one cell, X18. Upper third of the Trenton shales at Cannon Falls,
Minn.

19. Small portion of a large colony, <9, growing upon the concave side of Leptena alternata;
Cincinnati hills.
20. Two zoccia of same, X18. In the Cincinnati form of this species the zocwcia are more

inflated, and the whole zoarium more compact, and the growth more luxuriant than in
the typical Trenton form.

21. Several zocecia of another Cincinnati specimen, in outline, x18, showing the unusual
condition of three ‘‘gems” springing from one parent cell.
Figs. 22 and 23. STOMATOPORA TURGIDA UITriCh........0.06 0 cece cece ee teee cone eeeaeeecee teetevenes
An example of this species growing upon Pachydictya splendens Ulr., natural size and
same <9. Upper beds of the Hudson River gr., Wilmington, Il]. This species was
recently discovered in the lower part of these beds in Fillmore county, Minn.

Higs24. -PROROSCINA-TUMULOSA MS pisscwcaes Ged auiiseodyende te saeeiSeacaiw erades keecueen sarees eats
An example of this species, natural size and portion x9. Upper third of the Trenton
shales, St. Paul, Minn.

Figs. 25 to 27. BERENICEA MINNESOTENSIS UIrich. ........ ccc ccc cccnceceecaecececeue eeceuteuees

25 and 27. Two specimens of the natural size. Near Minneapolis, Minn. The original of
fig. 27 belongs to the Survey Museum. Reg. No. 5925.
26. (29 on plate) Portion of original of fig. 25, x9. (See also Plate II).

Fig. 28. PROBOSCINA FRONDOSA (Nicholson)...........ccccccceccvcuccaucecuececeeceenetececuuevens

Portion of specimen showing mural perforations very clearly, x18. Cincinnati gr., Cin-
cinnati, O.

114

116

117

117

118

119

120

119

*It is to be understood that when the collection containing the specimens illustrated on this and all of the following

plates of Bryozoa is not mentioned, they belong to the author.

‘
GCEOMOGTCAUNNT DN ALU RAL RHIS LOKRES URW EX @OF MIN NES OLACm
(Silurian Bryoza.)
Vol. HT. ee

 

 

 

 

EOU «0S delet Lith The Henderson Achert Lith.Co Cin.O
PLATE IL.

Fig. 1, BERENICEA MINNESOTENSIS Ulfiiiss sccvci neue cevedenneeves natieece eee sbene wise euniwe sirens
Small portion of the original of plate I, fig. 27, x18, showing zocecial apertures less con-
stricted than ugual, and portions of two non-celluliferous spots,

Figs. 2and 3. DIASTOPORINA FLABELLATA UIP ....-.-cccee cece cence eee e en ceee teen tenn este n ee neee ne
A complete zoarium of this species, of the natural size and <7, showing arrangement of
zocecial apertures, fine interstitial striz, and obscure concentric wrinkles. A small
tubiculous annelid is attached to the frond. Upper part of the Galena shales at Can-
non Falls, Minn. f
3. Portion of same X18, to show the characters of the species more clearly.

Figs. 4:t0.6.. MITOCLEMA (2) MUNDULUM: UO) 8) iic60ciecsecsire dis aces 8 eteoien tied SONS ERTET AV BOTTA VIS BEETS
4and5. Two fragments, nat. size and *9.
6. Original of fig. 5, 18.
Upper part of the Galena shales at Cannon Falls, Minn.

Fig; % ARTAROCLEMA, BILEINGSL Ulfisncccacesas a caceak aaa erwins d Soke Mee anne canes wats
View of the type of this species, natural size. (Introduced to show mode of growth pre-
vailing in this genus.) : ;
Trenton limestone, Ottawa, Can.

Figs. 8 to 11, 25, and 28 to 38. ARTHROCLEMA ARMATUM UIP. .......c cesses eee ce cece ee teee ee eesees

8. Large segment of the primary series, showing a sharply defined articulating socket; nat-
ural size and X18. This figure was inadvertently placed upside down.

9. Opposite side of another segment of the primary set, X18. This and the preceding
specimen is as thick as any noticed but not as long.

10. Complete segment of the secondary set, x18.

11. Upper three fifths of another secondary segment, finely preserved, x18. Upper part of
the Galena shales near Cannon Falls, Minn.

25. Vertical section, X25, of a primary segment somewhat doubtfully referred to this species.
Upper third of the Trenton shales, St. Paul, Minn.

28. Transverse section of a small segment (?secondary) X25. Cannon Falls, Minn.

29 and 30. Transverse and vertical sections of small segments found associated with the
original of fig. 25.

31 and 32. A transverse, and the lower half of a vertical section, X25, of full-grown primary
segments. Cannon Falls, Minn.

33. Vertical section of a secondary segment, eqally enlarged and from the same horizon and
locality as the preceding.

Figs. 12 to 15. ARTHROCLEMA PULCHELLUM BillingS.............. cece eee e eee e eee cee eet eneee eee
12. Vertical section of secondary segment, X25.
13. Transverse section of primary segment, X25.
14and15 Transverse. sections, X25, of two secondary segments, one with six, the other

with seven rows of zocecia. These sections were prepared from authentic examples.

collected at Ottawa, Can., from the Trenton limestone.
Figs. 16 to 21 and 23. ARTHROCLEMA CORNUTUM Ulr -

16. A continuous series of four primary segments, natural size, and three of them X7,
showing the articulating sockets near the base of each.

17. A similar series of segments, consisting of seven of the secondary order, natural size,
with fiive of them x7.

18 and 19. Two segments of the secondary order, X18, one with three cycles of zocecial aper-
tures, the other with four. They differ also in the ornamentation.

20 and 21. Opposite sides of rather small but very perfect primary segment, natural size
and X18. (See also plate III.)

23. ‘Transverse section of primary segment, X18, showing five rows of zoccia.
Middle third of the Trenton shales at Minneapolis, Minn.
Figs. 22 and 24. ARTHROCLEMA STRIATUM, D. SP........ccccccccccanceecccccceuaccteeeceuenseanes
Tangential section, X28, and tranverse section, X18. (See also plate ITI.)
Figs. 26 and 27. ARTHROCLEMA Sp. UNdEt.....-.... 0. ccc cece cece cccccuece seuuvavegaaueeecuaeeeuses

Two segments, the first incomplete, showing slight differences in ornamentation; X18.
Trenton shales near Fountain, Minn. :

12

12

19°

20:

19

20
TARURATL HUSRDI SURV ELT OF DIINO,

Ss

Den

©

PII.

(Silurian Bryozoa.)

Vol. Ill.

 

 

 

 

The Henderson -Achert Lath Co, Cin.O-

EOU.«C.S.del et. Lith

 
PLATE III.
PAGE

Figs. 1 to 3. HELOPORA DIVARICATA Ult................+: Peer en eee eee ee teen ene e ees 19:
. A segment of the natural size and x7, Minneapolis. Minn. | eae Pie
2. Portion of same, x18. Only three of the four rows of zocecia to be seen in this view have
been drawn. - . :
3. Transeverse section, X18, showing a spiral development of the zocecia.
Lower third of the Trenton shales at Minneapolis, Minn.

Figs. 4 to 6. HELOPORA SPINIFORMIS Ull......-.0seeeesee cece ersten rte nent nee e nee ee en eae tans 191
. A segment natural size, and lower portion of same *18.
5and 6. Vertical and transverse sections, X18.
“Glade” limestone at Lavergue, Tenn.
Fig. 7. ARTHROCLEMA ARMATUM UITP........:ceeeeeee cette rertee teens seeeres ett tteeenen ne ees 20:
A small segment supposed to belong to the tertiary set of this species, x18. Cannon
Falls, Minn. (See also plate II.)

Fig. 8. HELOPORA (2) Sp. UNdet.....-- ese eeee ee ere eee teen eee e nents etene sees ase e gas piea eats 191
Nearly entire segment, X18. Upper part of Galena shales, near Cannon Falls, Minn.
Fig. 9. HELOPORA ALTERNATA Ulr.......... ect sdee ahaa eth atsalaal i cles ectecage te deae sle t's leone SV Suma rer eG ssaek eave aie 19:

About three fourths of a segment of this species, x18. Middle third of the Trenton
shales, Minneapolis, Minn. Itis within the possibilities that these segments may
belong to the tertiary set of Arthroclema striatum Ulr.

Fig. 10. HELOPORA MUCRONATA UIP.....----ee eee seen eter een ee eee reee es Leste eens eeee scans seen 19.

A segment of this form natural size, and the greater part of it 18. The specimens
upon which this species is found may prove to belong to Arthroclema armatum Ulr.

Upper part of Galena shales, near Cannon Falls, Minn.

Figs. 11 to 12. HELOPORA HARRISI JaME€S..........ee cece eee cree eee nein eee ben eeeneeee nn es 19%
ll and 12. Two segments, natural size and <18.
lla. Portion of original of fig. 11, x50.
11b. Transverse section of a segment, X50.
Hudson River group, Waynesville, Ohio.
Figs. 13 and 14. ARTHROSYLUS CONJUNCTUS UlP..........2 ce eee e eet ene eet tne cen e ene n ees 18
13. Lateral view of the central portion of a segment, “18.
14. View of small portion of non-celluliferous side of same, *18.
Trenton shales, near Fountain, Minn.
Figs. 15 and 16. ARTHROSTYLUS OBLIQUUS UIP......-.--.. cece ee eee eee ene en eee ee reee ne eetees 18
Two views of a segment of this-species, X18, in the first showing the non-celluliferous
side with the upper extremity and about three-fourths of the length, in the second
the central portion turned so as to show the lateral aspect.
Lower third of the Trenton shales at Minneapolis, Minn. ;
Beneath fig. 15 a small figure is erroneously marked with the number, 16. This repre-
sents a transverse section of the type of the genus A. tenuis (J: ames), from the lower
part of the rocks at Cincinnati, Ohio,

Figs. 17 to 20. NEMATOPORA GRANOSA Ulr........ --- dig afisatiad Mow tea tatain styl o aetna eis one islet aia ado 20;
17. Portion of unbranched fragment, X18, showing the granulose angles and interspaces,
‘and narrow zocecial apertures; the latter in five rows.
18. Bifurcating fragment, X18, with the rows of granules slightly flexuous.
19 and 20. Portion of slightly worn fragment, and end view of same, X18. This has only
four rows of zocecia.
Upper part of Galena shales, near Cannon Falls, Minn.
Figs. 21 to 23. NEMATOPORA CONFERTA UIDP....... ccc ccc ce cee cece cece eee eee eee e tenes ete teee 20
Zoarium of this species, natural size, x9, and portion ofsame X18. Upper part of Galena
shales, near Cannon Falls, Minn.
Figs. 24 and 25. NEMATOPORA OVALIS Ulr..... 0... cece cence cee cece cree test enc eeeatenteasereentes 20
Two fragments of this opecies, natural size and x18, the first with four rows of zocecia,
the other with five. Upper part of Galena shales, near Cannon Falls, Minn.
Figs. 26 and 27 NEMATOPORA DELICATULA UIP.......... ccc cece eect cece ee beet enn e eens ee eeeteeanes 20
Two fragments of the exceedingly delicate zoarium of this species, natural size and
x18. Upper part of Galena shales, near Cannon Falls, Minn.

Figs. 28 to 33. ARTHROCLEMA STRIATUM, NeSpys inc uasinas awe aves ce mexavaosesas vias en eeeeesemeie o 19
28. ead segment, natural size and X12, with a large articulating socket and expanding
ends.

29. Lower end of same, X18.

30 and 31. Lateral and end views of a large and strongly striated primary segment, natural
size and X18. The zocwcial apertures are incorrectly represented in this figure. (See
correction p. 199, sixth line from top.) :

32 and 33. Two segments of the secondary set, natural size and X18. One has five cycles of
zocecia and an articulating socket, the other six cycles and no distinguishable socket.

(See also plate II.)
Middle third of the Trenton shales, Minneapolis, Minn.
Fig. 84. ARTHROCLEMA CORNUTUM UlP....... ccc cece cece ee teen ee eect ence ee se een e teen teeeneeeeeee 20
View of upper end of the segment represented by fig. 18 on plate II; x18.
Figs..35 to 3%. ARTAROCLEMA, SDP: UNCCb.. 6.060. ccc cecieees cos vaeesedeiawet es sateceanecobuseeteve gees 20

35. Slightly abraded segment, natural size and X18. An obscure, subcentrally situated,
articulating socket is distinguishable.
36 and 37. dg internal casts of the zocecia, X18, showing their spiral arrangement in the
segments.
Upper third of the Trenton shales, St. Paul, Minn.
CBROLIOGHOAT arm NATURAL HOSA SUV OF DARIN OLEA,

(Silurian Bryozoa.}

 

 

 

 

 

 

The Henderson Achert Lith.Co. Cin.0
EOU.«C.S.del et. Lith
PLATE IV.
PacE
Figs. 1 to 7, PHYLLOPORINA SUBLAXA, Ul?.........scece cece ec ee erence eees S pbashanieeewinint 86h as aa 201
land 2. Reverse side of small fragment, natural size and portion of same <9, showing
striated character of this side in young or exfoliated examples. Lower Trenton lime-
stone, Minneapolis, Minn. Survey Museum. Reg. No. 5954.
38and 4. Another fragment from the same locality, exposing the obverse side, natural size,
and portion of same x9. :
5. Tangential section, x18, showing appearance of zocecia at varying depths.
6. Two transverse sections of branches, X18. \
7. Arather loosely woven frond from the ‘‘Glade” limestone at Lavergne, Tenn.; natural size.

2

Figs. 8to 14. PHYLLOPORINA RETICULATA (Hal])........0. cece cece e cee cece etree teen ee ee nee eeenes 211
8. A frond exposing the reverse side, natural size, Minneapolis, Minn.
9. Portion of same, x9.
10 and 11. Another fragment from the same locality, natural size and x9.
12. Small fragment, likewise from Minneapolis, exposing the obverse face, X18.
13 and 14. Obverse and reverse sides of two fragments obtained from washings of Galena
shale at Cannon Falls, Minn.; X18.
15. Tangential section, X18, of an example from Trenton Falls, N. Y.

Figs. 16 to 21. PHYLLOPORINA HALLI UIP.... sce cece cece ce cence eee eens eee ne eens Riveadhe 6 areas 21:
16. Reverse side of aspecimen, natural size, showing irregulag arrangement of fenestrules.
17. Celluliferous side of another fragment, natural size, showing the irregular solid swellings.
18. Surface of same, x9.-
19. Reverse side of same, x9.
20. Tangential section, x18, cutting the zocscia just beneath-their mouths.
21. Another portion of same section, <18, where it divides the zoarium at a deeper level.
Upper third of the Trenton shales at St. Paul, Minn.
COLO CHB ATH any TARTRATE DOSRDIREC SRY DP ONES DDN,

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The Henderson Achert Lith.Co Cin.
E.0.U aC.S.det et Lith
PLATE V.

Figs. 1 to 10. PHYLLOPORINA CORTICOSA UITP....-... cece cee cette cent e een e neers ttn eee en een eees 21:
1. A frond of this species exposing the poriferous or obverse side; natural size.
2and 6. Reverse side of a fragment, natural size and a portion “9.
3and 7. Obverse side of another fragment, natural size and a portion <9.
4and5. Two specimens of the basal portion of the zoarium, natural size. ~
8. Tangential section, x18, cutting the zocecial tubes at varying depths from the surface.
9. Transverse section of several branches, X15.
10. Vertical section of a branch, X18.
Upper third of the Trenton shales, near Cannon Falls, Minn.

Figs 1land12. MRHINIDICTYA GRANDIS, D. SP... ee. ee eee eee erence nee ee eee eet e ete e ee tenn eennes 13
A fine example from the ‘Lower Blue” limestone at DixonII1I]., natural size and a portion
x9. (See also Plate VI.)

Figs. 13 to18. BHINIDICTYA MINIMA ULPl...... ccc ccc cece een ne cence eee ne tence eee eet aeeseeee 13

13. Three fragments of the natural size. «
14and 15. One of them x9, and a portion of same X18, showing the small zocecial apertures

and grano-striate character of the interspaces.
17. Tangential section of the variety MODESTA, X18, showing the appearences of the zocecia

at various depths beneath the surface.
18. Tangential section of the typical form of the species, X18.

Upper part of the Galena shales, near Cannon Falls, Minn.

Figs. 19 to. 21.. RAINIDICTYA PAUPERA, Ultic i sisicidcsesnincs vice sss tees eeetanew noses en waenesinaw cae 12
19, A nearly complete specimen, natural size.
20 and 21. A fragment, natural size x9 and 18.
Upper third of the Trenton shales, St. Paul, Minn.

Figs. 22 to 25. RHINIDICTYA NEGLECTA D. SP.... cece cee cee eee cece cece rece ce ee eens teen eeen gene 13
22. A fragment of the natural size and a portion X18, showing the usual characters of the
species.

23,24 and 25. Respectively, trarsverse, vertical, and tangential sections of a specimen wider
than the original of fig. 22, but agreeing in all other respects with it.
Trenton limestone near Danville, Ky.
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PLATE VI.

All the figurers on this plate except No. 18 are X18.

Figs. 1 to 6, 12and 13. RHINIDICTYA MUTABILIS Uli... ccc ccc eee ee ee eee ene eee ceag anes *125
1. Tangential section of an old and thick example of the usual form of this species. Figs.
‘6 and 12 represent transverse and vertical sections of same.
2and 3. Tangential and vertical sections of a fragment of the var. SENILIS (see p. 127), ;
showing the great abundance of the median tubuli and the structure of one of the
solid spots.
4and 5. Tangential and vertical sections of a well preserved and typical example.
6. Small portion of a transverse section prepared from the same specimen that furnished
the originals of figs. 1 and 12. ;
12. Vertical section of a thick specimen. (See figs. 1 and 6). Only one side of the zoarium
is entirely represented.
13. Tangential section of a young example.
For the external characters of this species see plate VII.
Middle third of the Trenton shales at Minneapolis and St. Paul.

Figs: 7 and 8. RAINIDICTYA FIDELIS: Ulfssccincese. ee esse einsinggues wees eke e 244 WOR Ca Eee ve nee 134
7. Tangential section, showing structure immediately beneath the surface; 7a, small por-
tion of same section showing appearances at the bottom of the vestibular region; 7b,
another portion of same, showing the form of the primitive portion of the zocscia and
the minutely tubular character of the walls and mesial lamine.
8. Vertical section of same specimen, showing well developed superior hemisepta.
Middle third of the Trenton shales at Minneapolis.

Figs. 9to1l. EURYDICTYA MULTIPORA Hall (?)........ cece e cece ee cece cee neste eee set eeaeeevaneus 139
Tangential, transverse, and vertical sections of a narrow frond from the upper third of'
the Trenton shales at St. Paul. (See also plates VII and XIV.)

Figs. 14 to 18. RHINIDICTYA TRENTONENSIS Uli... 0... 00. e cece cee eee cee e cee sete esuteeeeeeenes 135
14and 15. Transverse and vertical sections of a young example. .
-16and17. Vertical and tangential sections of a thicker specimen. In this each side is in
part composed of two distinct layers of zocecia. :
18. Primitive or prostrate portion of one zocecium of fig. 16, more highly magnified (50).
See also plate VII.
Lower third of the Trenton shales, Minneapolis, Minn.

Figs. 19 and 20. RHINIDICTYA GRANDIS, D. SD..... cece cee ee cece cere ee ce cece ne tees eteeeeeevenneens 136
Vertical and tangential sections of a specimen from the ‘‘Lower Blue” limestone at _
Dixon, Tl.

-
(Silurian Bryozoa.)

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EOU.a€.S.del et Lith.
PLATE VII.
PAGEs
Figs. 1to5, RHINIDICTYA PEDICULATA, D. SP.-seeeeeeeee eens yoke on ne ewe Rea VAN Gae Nemesia 13
1to4. Four specimens of the natural size, showing the mode of growth prevailing in this
species. Three of the specimens preserve the footstalk.
5. Surface of a slightly weathered example x9. In better preserved examples the nonpori-
ferous margins are much wider. (See description.)
Lower limestone of the Trenton formation, Minneapolis, Minn.

Figs. 6 to 9. HINIDICTYA TRENTONENSIS Ulr.... cee ee ee eee eee ee cee eee eter eee tenet e een ennes 13:
6to8. Three fragments of the natural size.
9. A well preserved fragment of the natural size and x9. ( See also plate VI.)
Lower third of the Trenton shales, Minneapolis, Minn.
Figs. 10 to 15 and 18 to 21. RHINIDICTYA MUTABILIS Ulr...... cece cece eee ee eee eee tee eee e ee ee 12
10. Surface of an old and excellently preserved fragment, x9.
11 to 14. Four representative specimens of the natural size. The original of fig. 11 belongs
to the Survey Museum; Reg. No. 5939. It is from the upper third of the Trenton shales
at St. Paul.
15. Portion of original of fig. 13, <9, illustrating the appearance of a large number of
specimens.
18. A finely preserved fragment, natural size and a portion x9. In this specimen the
zocecia are unusually small. :
19 to 21. A very young specimen (var. minor of my preliminary report,) natural size, a por-
tion <9, and several zocecial apertures X35. The margins are wide and sharp, the
outer zocecial apertures large and oblique, and the walls in the central part very
delicately granulose. (See also plates VI and VIII.)
Middle third of the Trenton shales, Minneapolis and St. Paul, Minn.

Figs. 16 and 17. RHINIDICTYA MUTABILIS, Var. SENILIS, D. VAP... ce ccc eee cee cece ee tees neon reece 12
A specimen of the natural size and a portion <9.
Middle third of the Trenton shales, St. Paul, Minn.

Figs. 22, 23, 25 to 28, and 32, RHINIDICTYA MALTABILIS, Var. MAJOR UIL...... eee cece eee ee eee 12
22 and 23. <A well preserved but narrow stipe of this variety of the natural size, and a few
zocecial apertures, with a portion of oneof the solid spots or macule, X18.
25 to 28. Four specimens of the natural size.
32, Small portion of the surface of the original of fig. 28, x9. (See also plate VI.)
Middle third of the Trenton shales, St. Paul and Minneapolis.

Figs. 24 and 29 to 31. EuryDICTYA MULTIPORA (?Hall).............. Lytle cae sie Yaiea Wiad deetiiamr atte y 13
24 and 30. A narrow, parallel-margined example of the natura! size and a portion x9. This
‘ resembles Rhinidictya mutabilis, var. major to such a degree that it was at first regarded
as belonging to that variety. :
29 and 31. A small, irregularly divided frond, natural size and a portion x9. This spec-

imen is evidently young, being thin and but inconspicuously maculuse. (See also
plates VI. and XIV.)

. Upper third of the Trenton shales at St. Paul, Minn.
GCEOMOGICAUANT DNA RAW APHIS LOR SURWVEREOFIMININES ODA
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Figs.

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PLATE VIII

PAGE.

1to3. RHAINIDICTYA MUTABILIS UIP.... 2... cece eee ere eee eee Ans dd Saneaten eS we Gppemreaines
Three portions of an old example of this species x9, showing, in 1, the thick, rounded
and granulose margin, in 2, the shape of the zocecial apertures at the upper extremity
of the specimen, and in 3, their form near the lower end of same. (See also plates
Vi and VII.)

4and 5. PACHYDICTYA PUMILA UIP... ccc cece cece cece ce teen ee teen teen nen n ee ere re tenesaseees
Two fragments of the natural size, and one of them representing the basal part of the
zoarium, x9. (See also plate X, and remarks on p. 158.)

6to10. RHINIDICTYA EXIGUA Ulr Lei juaneeivd Sindy hGS oh RRMA a eels ea's Gem tomes See ees
6and7. The basal part of a specimen of the natural size and x9. One of the branches has
three, the rest of the zoarium four rows of zooecia.
8. A delicate fragment with only three rows of zocecia,
9and 10. A branching fragment of the natural size and the lower half x9, This has from
five to seven rows of apertures.
Lower third of the Trenton shales at Minneapolis.
11 to 17. PACHYDICTYA ACUTA (Hall) and varieties. .... 00... ce cece cece eet eee e eee een eeeeees
Figs. 11 and12. A specimen of the natural sizeanda portion x9. Trenton limestone,
Trenton Falls, N. Y.
13. A very small specimen, with only six and seven rows of zocecia, from the Galena lime-
stone near Fountain, Minn.
14 to 16. Three specimens from the Galena shales near Cannon Falls, Minn.
17. Surface, x9, of a well preserved fragment from the same horizon and locality as the pre-
ceding. (See also plate IX.)
18 and 19. PACHYDICTYA ELEGANS, I. SP..... cc cccc ccc s eee e ee cence nec cence seceessseeveseeens

18. A very nearly perfect zoarium of this species, natural size, from the lower part of the.

Galena shales at St. Paul. Later collections show that this species is exceedingly
abundant at that locality and that the specimen here figured divides with greater
frequency than usual.
19. Enlargement of the beautifully ornamented surface of same, X18. (See also plate 1X.)
20 to 27. PACHYDICTYA OCCIDENTALIS. UL. « sececcnnnne cedenescsean aetavenswwenssreseerconce
20 to 24. Five specimens of the natural size, illustrating the variable character of the zoaria.
25. Surface of fig. 24, 9.
26 and 27. A frond of the natural size and a portion of its surface <9, traversed by irregular
grooves caused by interruptions in the development of the zocwcia. (Seealso plate IX.)
Upper third of the Trenton shales at St. Paul.
28 toia4. PACHYDICTYA. FIMBRIATA. UIs sous ov ewe ee seas dosueminsica de 8s ede tered eweee de ends
28 to 30. Three specimens of the natural size, the last one the widest seen.
3l and 32. A very narrow and seemingly young example, natural size and the upper part x9.
33 and 34. An excellently preserved fragment of the natural size and a portion x9. This pre-
sents the fully matured condition of the species. (See also plate IX.)
Middle third of the Trenton shales at Minneapolis and St. Paul.

126

151

131

154

151

152
BEDEDELBN EH avo VEN RAE TORRY SUL DEP MALONE DP
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The Henderson Achert Lith.Co. Cin.0
EOU 4C.S.del et Lith
PLATE IX.

Figs. 1 to 5. PACHYDICTYA FOLIATA UIP... .... cc cece cece etree eect eee e etree eeseneee tact reenaeeeee 149
1. Tangential section, X18, cutting the zoarium a little cpligtely, The figure which was
inadvertently placed upside down on the stone represents a spot of the section where
inequality of level caused the zoarium to be divided in such a manner that it brings
into rapid review the various changes from the base of the zocecial tubes to the surface.
The shaded and vertically lineate zone in the lower part of the figure represents the
median tubuli and lamine.
2. Tangential section X18, showing structure in the outer half of one of the layers of zocecial
tubes in a well preserved specimen.
Small portion of same X35, to show the minutely tubular character of the zocecial walls.
Vertical section, <18.
5. About two thirds of the width of a transverse section, X18,showing median tubuli very
distinctly. (See also plate X.)
Lower third of the Trenton shales, St. Paul and Minneapolis.

Figs. 6and 10. PACHYDICTYA OCCIDENTALIS UIP....... ccc cece cece cece eet ee ence een neee tone eeneee 151
6. Represents a small portion of a tangential section just beneath a bifurcation of the
zoarium, x18. At this point itis common to find, as in the present case, that the
longitudinal interspaces are wider and with more lines of median tubuli than usual.
10. Vertical section x18. (See also plate VIII).

Dao

Upper third of the Trenton shales at St. Paul. ‘a
Fig. 7. PACHYDICTYA ACUTA (Hall)..........ceceeeseee eee ee eens jest alt acer edee snerseeu ges Mewar 155
Tangential section of a specimen from Cannon Falls, Minn. (See also plate VII.
Figs. 8 and 9. PACHYDICTYA ELEGANS, D. 8D. ..cc ese c cece cece ee ce teen eee ne ce ee tenet eet eeeneees 154

8. ‘Tangential section. x18, cut obliquely so as toshow parts of both sides of the zoarium.
This specimen was very old and thick and in the outer part (upper third of figure) de-
veloped two extra lines of median tubuli in each longitudinal interspace. The end
spaces are also unusually long.

9. Small portion of same section, X35. (See also plate VIII).

Base of Galena shales, St. Paul, Minn.

Figs. 11 and 12. TRIGONODICTYA CONCILIATRIX ULP....... ccc cece ccc cece eect eee e ee eee ne eneeees 16(
11. Transverse section, X18.
12, Tangential section, X18, from a specimen ip an unusually good state of preservation.
(See also plate X).
Upper third of the Trenton shales near Cannon Falls, Minn.

Figs. 13 and 14, PACHYDICTYA FIMBRIATA UIl........... cece ce ceee eee e eects en teneeneeee teen cenees 15:
13. Tangential section, x18. At the upper end of the figure the section sinks to the level
of the median lamina.
14. Small portion of one of the longitudinal interspaces and adjoining walls of several zoce-
cia, X35. (See also plate VIII).
Middle third of the Trenton shales, St. Paul and Minneapolis.
CSUR IC DP VL

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The Henderson -Achert Lith.Co Cin 0

EoOU aCS dei ot Lith
PLATE X

Figs 1 to 4, PACHYDICTYA PUMILA UIP... ccc ccc cece ee enn cnet n ene nen nent eee nese nnneaee
1. A group of specimens of the natural size.
2and 3. Two fragments, natural size and <9, with some of the zocecial apertures closed.
4, The basal part of a rather young example, natural size and x9. (See also plate VIII).
Upper part of the Galena shales, near Cannon Falls, Minn.

Figs. 5 to 10. PACHYDICTYA FOLIATA ULL. -... cece cece cece cee tenet eee teenenee iodo baa Say gaa ae
5 to8. Four specimens of the natural size. Fig. 6 presents the unusual condition of raised
macule.
9. Surface of fully matured example, <9.
10. Surface of a young zoarium, X18. (See also plate IX).

Figs. 11 to 14. PACHYDICTYA TRISERIALIS UlY............ce eee ee eens cua eiasele's ial abdicia aiennanse«

11. Portion of a block of limestone with a group of the slender ramulets of this species,
natural size.

12. Surface of an old example, x18, on which many of the zocecial apertures preserve the
closures.

13 and 14. Two transverse sections, X25, the first prepared from a young example, the sec-
ond from one like the original of fig. 12. :

Trenton limestone, Montreal, Can.

Figs. 15 to 20. TRIGONODICTYA CONCILIATRIX UIP... ee cece cece cece eee tener eens eee eee eee eneee

15 to 19. Fivespecimens of the natural size, illustrating the zoarial variability of the species.

20. Surface of well preserved example x9. (See also plate IX.)

Upper third of the Trenton shales near Cannon Falls, Minn.
Figs. 21 to 25. STICTOPORELLA CRIBROSA ULl..... ccc. cccee cece ce eece essence ceeeeeeeeeeaeens aeees

21. Nearly complete zoarium of the prevailing type of this species, natural size.

22. A thin fragment less regularly developed than usual.

23. Surface of an excellently preserved example, 9.

24, Another portion of same X18. In this specimen the mesopores are very numerous.

25. Tangential section of an average specimen, X18. In the upper part of the figure the
section descends to the level of the prostrate portion of the zocecial tubes. (See also
plate XI.) ;

Middle third of the Trenton shales at Minneapolis.

14

15!

16!

18
CUO DOEGHBN haw WAT b PORE SULA YC OL? OOPS ABS
( Bryozoa.|
Vol. H. PIX.

 

 

 

 

 

 

E.0 U.&C.S.del.et-Lith. The Henderson -Achert Lith.Co. Cin.0.
PLATE XI.

Figs 1 to 3, 6, and 8 to 11. STICTOPORELLA ANGULARIS UIP..... ccc cece eee cee eee ee eeecenenaee 18:

1to3. Three specimens of the usual form of this species, natural size.

6. Surface of an average example, x9.

8,10and 11. Tangential, transverse, and vertical sections, X18, prepared from the oldest
example at hand. “

9. Small portion of a tangential section X50, showing the minutely tubular character of the
divisional line between adjoining zccecial walls.

Lower third of the Trenton shales at St. Paul and Minneapolis.

Figs. 4,5and 7. STICTOPORELLA ANGULARIS, Var. INTERMEDIA, Nl. Var...... cece cece eee eee eens 18:
4, A small subfrondescent example from the base of the shales at Minneapolis.
5. A fragment of the usual form of the variety from tne same horizon in Fillmore county.
7. Surface of same X18, showing the extreme paucity of mesopores and in the upper left
corner a portion of one of the clusters of thin-walled zocecia.

Figs 12 to 19. STICTOPORELLA FRONDIFERA UIP... ccc cece cee cee eee cence nee eee teen eeeene 18:
12 to 14. Three specimens of this species, natural size. The original of fig. 14 belongs to
the Survey Museum. It is oneof a number bearing the register number 5946.
15. Surface of original of fig. 12 x9.
16. Tangential section of an average specimen, X18.
17. Small_portion of same section x50, to show the structure of the inter-zocecial lines.
18. The basal or prostrate portion of several zocecial tubes as Shown in another tangential
section, X18.
19. Vertical section, x18.
Lower third of the Trenton shales at Minneapolis.
Figs. 20 and 21. STICTOPORELLA RIGIDA UIP... .... 2. cece ee cece eee scence eeee sn eueeeeeeeesagens 18¢
, 20. A fragment of the natural size and the greater part of it <9.
21. Portion of same, <18.
Lower part of the upper third of the Trenton shales at Fountain, Minn.

Figs, 22 and 23. STrICTOPORELLA CRIBROSA UlQ......... cc ccee cece ccc ce tenn n eee eeseseetereteneaees 184
22. Vertical section, X18.
23. Transverse section, X18. (See also plate X).
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The Henderson -Achert Lith.Co. Cin 0.

E.0U «C.S.del. et. Lith
PLATE XII.

Figs. 1 to 4,30 and 31. ODHESOHAROPORA ANGULARIS, I. SP.eeesecese cece scene cence eee eeeteenenenees
land 2. A small specimen of natural size and the greater portion of it x9.
3and4. A large specimen of the natural size and a portion of the upper half of its sur-

face X18.

30 and 31. Vertical and tangential sections, < 18.

Trenton limestone, Minneapolis.

Figs. 5 to 29. ESCHAROPORA SUBERECTA ULV......ccc ccc cece eee cece ene nee eeet ene eet eeeteeteeens
5to17. A series of specimens, most of them above the average in size and the four last

with from one to three rows of monticules.

18and 19. The central and basal portions of the original of fig. 9, <9.

20.

21,

22.

23.
24,

25.
26.
27.

28.
29.

Part of same, X18. The characters as shown in this specimen are to be regarded as
typical for the species in its younger stages.

Surface of another small example, X18, with the marginal rows of zocecia unusually
conspicuous.

Surface of the basal third of the original of fig. 15, X18. The features here presented
are unusual.

Surface of the upper part of the original of fig. 16, X18.

Surface of the original of fig. 17, x18. In the specimen the zoccial apertures manifest
a tendency to arrange themselves in an obscurely pinnate manner.

Tangential section of an example corresponding to fig. 9; 18.

‘Tangential section of a specimen of the size of fig. 8, or a trifie larger; X18.

Tangential section, X18, showing the appearance just beneath the surface of au old
example;

Vertical section of several zocecia prepared from an average specimen, X18.

Transverse section of same X12.

Middle third of the Trenton shales at St. Paul and Minneapolis.

16
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Figs.1to1l. EscHAROPORA CONFLUENS, 0 SP......--eeeeeees Sea weauiala 6G 4s 44 ule saat Seclect Gita sis ea 171
1. A specimen that preserves the pointed articulating base; natural size.
2. Well preserved fragment, the surface of which is enlarged in fig. 5.
3. Portion of a large specimen with comparatively remote bifurcations and obscure monti-
cules; natural size.
4. Incomplete basal part of another large zoarium; natural size.
5. Surface of the original of fig. 2, x9. The line above indicates the contour of the surface
in a transverse section.
6. Tangential section, x18, of a well preserved example. The figure embraces about two-
thirds of the width of the branch, the right side being marginal.
7. Several zocecia of the same section, 35, showing the mural lineation.
Another portion of the same section, 18, showing the prostrate part of the zocecia.
9. Left half of another section, X18, prepared from a specimen in a less favorable (the usual)
state of preservation. In thisexample the marginal zocecia were uncommonly large
10 and 11. Transverse and vertical sections x18.
Middle third of the Trenton shales at Minneapolis.

ge

Figs. 12 and 13. EscHAROPORA (?) LIMITARIS, 0 SDP. OF Val....... cesses eeeee shicombdiacaneanier stages. MNT?
12. A very large specimen, provisionally referred to this species; natural size. Middle
third of the Trenton shales at Minneapolis. Survey Museum. Reg. No. 5930.
13. A specimen of the average size of the species as it occurs in the lower third of the
shales at Minneapolis. (For internal structure see figure 9 on page 172.)

Figs. 14 t0 17. PHNOPORA INCIPIENS, D. SP.-... cece cece eee eee eee e cet e eee eeeneeeeeneeeesees 174
14. A fragment of the natural size and a partof it X18. Trenton limestone, Montreal, Can.
15. The basal part of a zoarium from the Trenton limestone at Chimney Point, Vermont.
16. Tangential section, X18, of a specimen from Montreal.
17. Tangential section of another specimen from Montreal, X28, showing structure imme-
diately beneath the surface.

Figs. 18 to 21. STICTOPORELLA EXIQUA, Nn. sp.*
18. Portion of the delicale zoarium of this species, natural size.
19. Surface of one of the branches x18.
20. Tangential section x28.
21. Transverse section <18.
Trenton limestone, Montreal, Can.

Figs. 22 to 26. PH@NOPORA WILMINGTONENSIS, D SD..cs.. eee eee e cece en cece ceeeenceceueucesenuns » 175

22. Fragmentary example of the natural size.

23. Surface of same x9.

24. Two portions of a tangential section, x18, the upper showing the appearance just
beneath the surface, the lower just over the prostrate part of the zocecial tubes.

25. One of the zowcia and portions of the adjoining ones <35 to show the minute structure
of the walls.

26. Vertical section, x18.

*The description of this interesting species having unfortunately been omitted from its proper place in the text, the
following brief diagnosis of its peculiarities is added here:

Zoarium consisting of slender and frequently dividing branches, not exceeding 1.5 mm. in width; margins parallel,
scarcely sharp. Zocecial apertures oval, more or less oblique, arranged in eight or nine longitudinal rows, six or seven in3
mwm., between longitudinal ridges; diagonally three or four inl mm. End interspaces two or three times as long as the
width of the space between the ridges, rsling distally, usually with two elongate shallow pits or furrows.

All that is known of the interior is shown in the figures.

The types were collected at Montreal, Canada, in the Trenton limestone, by Mr. T. C. Curry, for the Peter Redpath
Museum, from which institution they were obtained by the author in exchange for other fossils,

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1. A fragment with subparallel margins, natural size.

2. Surface of same 9.

3. Two rows of apertures X18; shows the papillose character of the ridges.

4. Vertical section, x18. By an oversight the diaphragms are wanting in this figure.
Each tube should have one crossing it at right angles at a point about midway between
its aperture and the mesial line.

5. Tangential section x18, The internal characters are but illy preserved in even the best
of the specimens sectioned.

6and7. Old zoarium of the natural size with a portion of its surface x9. With age the
macule become more distinct and the longitudinal arrangement of the zocecial aper-
tures less obvious. :

8. Portion of a zoarium larger and wider than usual; natural size.

Middle third of the Trenton shales at Minneapolis.

Figs. 9 to 11. EURYDICTYA MULTIPORA (?Hall, SP.)........cee cece cece erect eee nner nee ene eceeee

9. Fragment of a slightly undulating expansion, natural size.

10. Surface of same, 9.

11. Small portion of same, x18.

Upper third of the Trenton shales, St.. Paul. Survey Museum, Reg. No. 5942.
Figs. 12 to 21. ARTHROPORA SIMPLEX UITP..... cee c ccc c ccc e eee erect eee e erence ne ee ee eee e ten eens

12. Two segments of the usual size.

13 and 14. Two bifiurcating segments, probably abnormal; natural size.

15. Several segments preserved in their natural positions, natural size.

16. Surface of a well preserved fragment, x18.

17. Several zocecial apertures of same, X35. In many specimens the longitudinal prolon-
gations from the ends of. the inner ring of papille are longer, in some cases even
joining.

18. Irregularly divided basal joint, natural size.

19. The lower part of same, x9. It is difficult to make out the apertures, the whole sur-
face appearing to be covered with closely intertwining stria.

20. Vertical section, 18. showing the form of the zoccia, the hemisepta, and other fea-
tures.

21. Three portions of a tangential section, x35. In a the right hand third shows the struc-
ture just beneath the surface. Inthe middle third the section sinks to the level of
the prostrate part of the zocecia and in some of them both kinds of hemisepta are
shown. On the left side the dark band represents the noncelluliferous margin. In
c we have only the prostrate part of the zocecia and the dense margin.

Middle third of the Trenton sRales at Minneapolis. .

Figs. 22 to 25. ARTHROPORA BIFURCATA, I. SP...see eee cece rece e eee ee tee erence eee erence eee eneeee
22. A small segment natural size and its upper part X18.
23 and 24. Two old segments, the last one probably the basal, of the natural size.
25. Surface of the original of fig. 28, x18, illustrating the aged condition in contrast with
the youthful stage represented in fig. 22.
Upper third of the Trenton shales, St. Paul.

Fig. 26. ARTHROPORA REVERGA, D. SD..-...+e+-00: AUREead. cet ave geue Sota akdaneo a meeratos
Natural size view of an average segment, and a portion of its surface x35.
Base of the Galena shales at St. Paul.

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Figs, 1 to 6. MONTICULIPORA (?PRASOPORA) GRANDIS ULL... ...... eee e sec e eee eee r eens cee eeee cece 21
1. A small lobate mass of the natural size.

Fragment of a subramose example, natural size.

Surface of same X9.

Several zocecia of same, X18, exposing the cystiphragms.

Tangential section <18.

Three portions of a vertical section, X18, showing extremes of variation in the tabula-

tion of the zocecial tubes. Mus. Reg. No. 5969.

Base of the Trenton shales at Minneapolis.

Figs. 7and 8. MONTICULIPORA WETHERBYI PUITICD........ ccc eee cee cece ee eee tetera ee enne 21
Tangential and transverse sections, X18, of a specimen from the Trenton limestone at

Minneapolis. Mus. Reg. No. 5967.

Figs. 9 to 12. MONTICULIPORA INCOMPTA, D. SP... cece cece cece ence eceee tenes BoPaviotamenadacedes 21'
9. Tangential section X18.
10. Small portion of same 50, showing the peculiar structure of the walls.
ll. Vertical section X18.
12. One of the walls X50.
Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5968.

Figs. 18 to 15. ATACTOPORELLA INSUETA, D. Sp..... IRR bse oY Sis Vou ONES RERE REN ES oR ee Sheet 22:
13, <A crinoid column covered with the zoarium of this species, natural size.
14. Tangential section X18.
15. Portion of same x50. (See also plate XVIII.)
Middle third of the Trenton shales at Minneapolis. Mus. Reg. No. 5985.
Figs. 16 and 17. ATACTOPORELLA TYPICALIS, Var. PRASCIPTA, D. VAl...... cece cece ee eee e eee eceeeene 22.
16. Vertical section <18.
17. Tangential section 50. (See also plate XVIII.)
Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5984.

Figs, 18 to 21... ATACTOPORBLDA, CRASSA, Di SPs. saaneensaa eee soba eeeladueldewulieien sane pt Ve be davoneales 22
18. Tangential section <18.
19. Small portion of same, X50, showing the structure immediately beneath the surface of a
matured example.

20. Another portiou of same 50, showing the appearance at a deeper level in the zoarium.
21. Vertical section, x18.

Galena shales near Cannon Falls, Minn.

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Figs. 1 t0 10. PRASOPORA SIMULATRIX UIL...... ccccccec cence ence eee eeeen eee eetanenees acecare besReheiaie

land 6. Vertical and tangential sections, x18, of a specimen of the var. orientalis from
Trenton Falls, N. Y.

2and7. Similar sections of a Canadian (Ottawa) example of the same variety.

3and8. Similar sections of a Kentucky specimen of the western or typical form of the
species.

4and 9. Vertical and tangential sections of a specimen from the lower part of the Galena
limestone at Mantorville, Minn. Mus. Reg. No. 5986.

5and 10. Similar sections of another example of the typical form of the species from the
upper third of the Trenton shales at.St. Paul.

Figs. 11 to 15. PRASOPORA CONOIDEA ULL...... 0.0 cece cece ence e eee nee eee eee nee eee ee eens ens

11 to 13. Lateral, basal, and one sectional view of three specimens of this species, natural
size.

14. Tangential section X18, showing the thin walls and minute acanthopores which are
characteristic of the species.

15. Vertical section, X18. The abundant tabulation of the tubes is the chief peculiarity
brought out by this kind of section.

Upper third of the Trenton shales near Cannon Falls, Minn.

Figs 16and 17. PRASOPORA SELWYNI Nicholson.......... 0c ccc ee cece cece eee cen tenet e none rene ones
16. Vertical section 18, showing the isolation and semi-circular form of the cystiphragms.
17. Transverse section of same X18. :
Upper part of the Galena shales near Cannon Falls, Minn.

Figs. 18 and 19. PRASOPORA INSULARIS, Var. FILLMORENSIS, I. Var... cece een cece seer e eee ee cee
18. <A tangential section <18, showing the different appearance of the inter-zocecial spaces
when compared with typical P. insularis.
19. Small portion of a vertical section X18, showing the vesicular character of the inter-
spaces to which is due the difference referred to in the preceding paragraph.
Probably from the Trenton shales near Fountain, Minn.

Figs. 20 to 23. PRASOPORA INSULARIS, I. SP... ce cce cece cece erence eee e nee e sence eee cane reese eee eee

20. Tangential section of an excellently preserved specimen, X18.

21. Small portion of same 50 to show the minutely cellulose character of the walls.

22. One zoccial tube with adjacent mesopores and one wall with adjoining cystiphragms
and diaphragms, X18. In showing the much greater abundance of the cystiphragms
and diaphragms when compared with other species of the genus, this figure, though
small, is sufficient for the identification of the present species.

23. Small portion of another tangential section, X18, in which the zocecial tubes aré more
frequently in contact than in fig. 20.

Galena shales near Cannon Falls, Minn.

Figs; 24 to 26: PRASOPORA CONTIGUA. Ulbiiiiiccwisew scories ese, Steno ede ¥OeG weve bedwaWed does es F
24 and 25. Vertical and tangential sections, x18, of a specimen from the upper part of the
Trenton shales of Goodhue county, Minn.
26. One zocecium and adjoining mesopores of same x35. Mus. Reg. No. 5989.

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PLATE XVII.
Figs. 1 to 8. MEHSOTRYPA INFIDA ULl......cccccccccaccsceeeeeteeeeeseccsseeececeeengettseeeteen eens

land 2. Two tangential sections prepared from the same example, X18. The first illus-
trates the fully matured condition, the second an earlier level in the zoarium. Tren-
ton shales near Fountain, Minn.

3to5. Three portions of a large vertical section of the same, X18, showing the variable
disposition and appearance of zoccial diaphragms.

6. Portion of another vertical section of same X18. Mus. Reg. No. 5993.

7. Surface of same, <9, showing a condition approximately intermediate between figs. 1
and 2.

8. Surface of a parasitic specimen in a condition corresponding with fig. 1. Middle third
of the Trenton shales, Minneapolis.

Figs. 9 to 12. MESOTRYPA (?) SPINOSA, D. SP... .ccee cece cece e teen een e eee ei eee renee ner eeeenes
9. Surface of well preserved example, showing the round form and regular arrangement of
the zocecial apertures, and the strong acanthopores; 9.
10 and 11. Tangential section, X18, and parts of several zocecia x50.
12. Small portion of a vertical section, X18, showing unmistakable cystiphragms in the
lower half. Other parts of the same section are like figs. 3 and 4 of this plate.
Middle third of the Trenton shales at St. Paul and Minneapolis.

Figs. 13 to 21. ASPIDOPORA ELEGANTULA, I.SDeseescccscccee cee cent cece cece ee ete een eee eeee tees
13. A fine example of this species on the surface of which an intermittent second layer of
zocecia was forming; natural size.
14. One of the areas of the secondary layer, <9.
15. Tangential section prepared from the primary layer of same, x18.
16 and 17. Views of the upper and lower sides of a specimen that consists of at least four
distinct layers grown loosely over each other; natural size.
18. Upper surface of same, <9.
19. Tangential section of one of the layers of same, X18.
20. Parts of several zocecia of a tangential section, <50.
21. Several zocecia and mesopores as seen in a vertical section of one of the layers, 18.
Galena shales, Kenyon, Minn. These two specimens were collected by W. H. Scofield
and kindly presented by him to the author.

Figs. 22 to 25. PRASOPORA LENTICULARIS, D. SP.... se cece cece etc ee teen cere reece te neeetees ence

22. Upper surface and sectional view of an example of this species; natural size.

23. Two portions of a tangential section of same, X18, the upper half representing the ap-
pearance in the upper third, the lower half that in the basal third of the zoarium.

24. One of the zocwcia and adjoining parts of same, X50.

25. Vertical section of same, X18, showing the comparatively loose tabulation of the two
sets of tubes.

Upper third of the Trenton shales at St. Paul.

Figs. 26 to 32. ASPIDOPORA PARASITICA Ul?......... ccc cee e ce erence eect ceenttceseneeeceeneees
26 add 27. Portions of a tangential section, x18 and <50, with few cystiphragms mats zocecia
very slightly larger than usual.
28. Vertical section of same specimen, X18, showing entire thickness.
29. Surface of same, x9.
30 to 82. Tangential and vertical sections, X18, and the surface 9, of a thicker zoarium.
Lower third of the Trenton shales, Minneapolis and near Fountain, Minn.

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PLATE XVIII.
PAGE.

Figs. 1 to 4. ATACTOPORELLA TYPICALIS, Var, PRACIPTA, 0. Var....e-eeeeeeeees Shee as Bare saneees 223
land 2. Tangential and vertical sections of a thick expansion, x18.
3. Surface of well preserved specimen, X18.
4. A montiferous variety attached to the shell of Orthis subequata Conrad. (See also plate
XV.)
Middle third of the Trenton shales, St. Paul.

Figs. 5 to8. ATACTOPORELLA INSUETA, D. SP....+-e-eeeeee pee eee Seren Coes Haro RET ES EB eS 224
5and6. Vertical and tangential sections of an example that is typical for the species in all
respects excepting that the acanthopores are less numerous than usual; X18. (See also
plate XV.)
7and 8. Tangential section and surface X18, of a variety with larger zocecia than the typi-
cal and common form of the species.
Middle third of the Trenton shales, Minneapolis.

Figs. 9 to 20.. HOMOTRYPELLA INSTABILIS Ulr...... ccs cece eee c cence nese eee cence ee ceeeceennees 22
9tol1l. Three fragments of the natural size, showing extremes in the size of the branches.
12. Surface of well preserved example X18, with the mesopores open and distinctly visible

and the walls thin.

13and15. Tangential and vertical sections X18, prepared from the original of fig. 9. The
walls are thick in the peripheral region and very few cystiphragms are noticeable in
the tangential section.

14. Small portion of same tangential section <50 to show the minute structure more clearly.

16. Central part of a transverse section of same specimen, X18.

17 and 18. Vertical and tangential sections X18, of a specimen with two series of cystiph-
ragms, thinner walls, much larger macule, and more abundant acanthopores than the
preceding.

19. Portion of one of the clusters of mesopores X50.

20. Several zocecia of thesame tangential section X50.

Middle third of the Trenton shales, St. Paul and Minneapolis.

Figs. 21 and 22. HoMOTRYPELLA MULTIPORATA, D. SD.... cece cece eee eee eee ete e ence tenet neneee 230
21. Tangential section x18, showing, among other peculiarities of the species, the abun-
dance of the mesopores.
22. Peripheral part of a vertical section X18, showing the comparatively remote tabulation
of the tubes.
Middle third of the Trenton shales, St. Paul.

Figs. 23 to 30. HomoTRYPELLA (?) OVATA, NSD........5- RAINE Gaels bas a6 Mote sade wee SE 231
23 to 26. The basal part of a zoarium and three representative branches of the natural size.
27. Well preserved fragment of the natural size and a portion of its surface X18.
28 and 29. Verticaland tangential sections X18.
30. One zoecium and adjacent parts of the tangential section, x50.
Galena shales near Cannon Falls, Minn.
Figs. 31 to 33. HomMorrYPELLA RUSTIOA, n. sp
31. Vertical section <18.
32. Two portions of a tangential section X18, the upper part giving the appearance imme-
diately beneath the surface while the lower represents a deeper level.
33. Small portion of the mature region of the tangential section x50.
Upper part of the Hudson River group near Spring Valley, Minn.
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PLATE XIX.
PAGE

Figs. 1 to9. HOMOTRYPA MINNESOTENSIS U1r.... co. cece cece eee eer e erence ener enter eeeneneees 23:

1to3. Vertical, transverse and tangential sections X18, of a specimen having the walls in
the peripheral region thicker than usual. Mus. Reg. No. 5970.

3a. Small portion of a tangential section of an example of the var. montifera, x50. Base
of the upper third of the Trenton shales at St. Paul.

4and5. Tangential and vertical sections of an average specimen, X18.

6. The peripheral part of two zoccial tubes, x18, more closely tabulated than usual. Mus.
Reg. No. 59706.

7and 8. Two examples of the natural size. The end view under the latter shows the ex-
ceeding narrowness of the peripheral region.

9. Surface of the original of fig. 7, <9.

Lower third of the Trenton shales, Minneapolis.

Figs 10 16:16. HOMOTRYVPA BSILIS: WlP ve vias ov tciean wines 6 gates cette earn Bese sau sodas 23€
10 and 11. Two fragments of the natural size.
12. Vertical section X18. .
13. Tangential section in a pre-mature condition, <18.
14. Tangential section showing fully matured characters, X18.
15. Portion of fig. 14 more highly magnified.
16. Portion of fig. 13 more highly magnified.
Lower third of the Trenton shales at Minneapolis.
237

Figs..17t0 20: HOMOTRY PA. SEPARATA,D 8D o6cas-<ssisiccs eee ssicd SAW hie daciuigenine sist ei as Salew eee oak es
17and 18. Tangential section of this peculiar | Bpecles, X18, and a portion of same x50.
19. Surface of a well marked specimen x9.
20. Vertical section X18. Attention is to be directed to the tabulated interstitial spaces.

Lower third of the Trenton shales, Minneapolis.

Figs. 21 to 28. HOMOTRYPA SUBRAMOSA UID. ........ 6000 cece cece eect e ence tect sees teeeeerseenenace 229

21.. View of a characteristic specimen showing the irregular division of the branches.

22, 24 and 25. A series of three tangential sections x18, agreeing in all respects except that
while in the first the acanthopores are numerous and well developed they are fewer in
the second and quite inconspicuous in the third. Original of fig. 24 belongs to Survey
Museum, Reg. No. 5980a.

23. Small portion of fig. 22 more highly magnified.

26. Vertical section X18, of a specimen having the outermost region loosely tabulated; very
unusual. Mus. Reg. No. 5980b.

27. Vertical section of a typical example, x18.

28. Surface of an average example, showing the cystiphragms in the zocecial apertures, <9.

Upper third of the Trenton shales, St. Paul and near Cannon Falls.
 

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PLATE XX.
PAGE

Figs. 1 to 9,13 and 14. MONTICULIPORA ARBOREA, TD. SP.... see e cece reece teen een et ee te eeeneeeee 22;

1. Peripheral part of a vertical section <18.

2. Several tubes from the axial region of same X18, showing the presence of cystiphragms in
even this portion of the zoarium.

3. Transverse section from the center to the periphery of a branch X18, proving the presence
of cystiphragms throughout.

4and 5. Fully matured portion of a tangential section x18 and a small part of same 50.

6. Shows the appearance at a slightly lower level than fig. 4.

7. Small portion of the surface of the specimen represented by fig. 8; <9.

8 and 9. Two fragments of the natural size exhibiting a difference in the prominence of
the monticules.

Galena shales near Cannon Falls, Minn.
13and14. Tangential and vertical sections of a form of thespecies from the Trenton at

Rurgin, Ky.; X18.

Figs. 10 to 12. MONTICULIPORA (?) CANNONENSIS, 0. SP.... cece ce cee eee cece eee eee ree eee eeeeenae 22)
10 and 11. Vertical and tangential sections x18.
12. One zocecium X50.
Galena shales near Cannon Falls, Minn.

Figs. 15 to21. HoMOTRYPA CALLOSA, D.SP.... cece eee e ccc eet ee eee ee ene cece ease eens pian wiieaae 24:

15 and 16. Tangential sectionx18 and a small portion of same X40, of a specimen from the
Galena shales near Cannon Falls.

17. Vertical section of same X18.

18 and 19. Peripheral and axial portions of a vertical section <18, prepared from a specimen
from the Trenton at Burgin, Ky.

20 and 21. Tangential section of same X18 and X50, differing slightly from that of the Min-
nesota form.

Figs. 22 to 27. ATACTOPORELLA RAMOSA, D.SD....) cece cece eee ce een cee n eee cee teeesescnsceneees 22¢

22. Two portions of a tangential section X18, exhibiting differences that depend upon the
varying depth at which the section passes through the zoarium.

23. Small portion of same more highly magnified.

24. Axial region of a transverse section X18.

25. Vertical section x18, showing the continuance of the series of cystiphragms into the
axial region.

26 and 27. Two specimens of the natural size.

Upper third of the Trenton shales near Cannon Falls, Minn.

Figs 28 to 33. HOMOTRYPA SIMILIS FOOrd®......... ccc cece cece ccc eee ccc ents eens ceneeenveesnneeteeucuns 24:
28. Portion of the peripheral third of a transverse section X18, Cannon Falls.
29. Vertical section of an authentic Canadian example of the species x18.
30. Two portions of a tangential section of same x18. - i
31 and 32. Vertical and tangential sections of a Minnesota specimen, x18.
33. Surface of another specimen from this state x18.

Trenton limestone Ottawa, Can., and upper part of the Galena shales near Cannon
Falls, Mion.

 

*The systematic position of this species is doubtful. Though falling in a loose way under Homotrypa some of its char
acters are so peculiar that it can in no wise be regarded as a true representative of the genus. Thin sections are suggest
i vely like those of Homotrypella instabilis and in some features also simulate those of Eridotrypa mutabilis. ;
 

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PLATE XXI.

Figs. 1 t0 7. CONSTELLARIA VARIA, D.SD...cceeeeecee renee cece cer eeeees ser tenee erase teen eeee sense

1. Surface of a mature example, x9, with wide interspaces and correspondingly narrow
zocecial apertures.

2. Surface, x18, of another example showing a less matured stage than fig. 1, the inter-
spaces being thinner and the zocecial apertures larger.

3. Tangential section, x18, showing appearances immediately beneath the surface of an old
specimen. At deeper levels the walls are thinner and the interspaces narrower.

4, Small portion of preceding, x50, with two of the minute mural tubuli.

5. Vertical section of an average specimen, X18.

6and 7. Two fragments of the natural size, one very small, the other of medium dimen-
sions.

Galena shales near Cannon Falls, Minn.

Pace.

Figs. 8 to 12. NICHOLSONELLA PULCHRA, I. SD....c sce seee cece tee c ee ee ne ee cane ene eceeeettcteereeee
8. An unusually wide fragment of the natural size.
9. Surface of same, x9.
10. Two portions of a tangential section, X18, the upper illustrating the appearance just
beneath the surface of a mature example, the lower at a deeper level.
11. Vertical section of same, x18.
12. Central portion of a transverse section, 18.
“Pierce limestone”, Murfreesboro, Tenn.

Figs. 13, 14, 20 and 22. NICHOLSONELLA PONDEROSA ? UITiCh........... cece cece cece ence renee ee caees

13. Two portions of a tangential section, X18. In the original the details are obscure and
it is probable that the interstitial dots are too numerous and small.

20. Small portion of the peripheral part of a vertical section, X18. The structure is but
illy preserved in these sections.

14. Two portions of a tangential section of another specimen, 18, the upper immediately
beneath the surface.

22. From the peripheral part of a transverse section of same, x18.

. Lower third of the Trenton shales, Minneapolis.

Figs. 15 to 19 and 21. NICHOLSONELLA LAMINATA, D. SP...-eeee cee eee a sikh gianalapncev aye aParscatete aaa euseandae
15. Tangential section of specimen in an unusually good state of preservation, X18.
16and 17. Portions of same X50.
18 and 19. Under side of a fragment, nat. size, and the upper surface x9. In this specimen
the mesopores are shown much more clearly than in others.
21. Small portion of a vertical section, X18, passing through one of the maculae.
Middle third of the Trenton shales, Minneapolis.

Figs. 23 to 40. TREMATOPORA ? PRIMIGENIA (and varieties) Ulrich............ ccc ccc ee cee ceneeees

23 to 27. Fragments of the typical form.

28 and 33. Original type of 7. ornata and surface of same X18.

29. A large specimen of var. sp¢nosa ; 30, a smaller and better preserved fragment; 35, sur-
face of the latter, <9; 36, small portion of same x18.

31. Surface, <9, of an average example of the typical furm. No attempt has been made to
draw the small acanthopores.

32. Surface of specimen with acanthopores unusually abundant and inflecting the zoccial
apertures, X18, The specimen is peculiar also in having many of the mesopores open.

34. Original of fig. 26, x18, (var, ornata) with spines and occasional open pores in the inter
spaces.

37. Tangential section, X18, from aspecimen whose surface is drawn in fig. 32.

38. More common appearance of typical tangential sections, <18.

39. Small part of preceding x50.

40. Vertical section of basal expansion, X18. It is attached to a crinoid column and shows
how the tubes grew into the depressions between the rings and failed to attain ma-
turity.

Middle third of the,Trenton shales, Minneapolis,

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PLATE XXII.

1to3. Three typical specimens of the natural size.

4, Surface of the original of fig. 3 x9.

5. One of the depressed spaces of same X18.

6and 7. Two fragments, one unusually slender the other thicker than usual.

8. Portion of the original of fig.7 where the walls are thinner and the mesopores larger than

usual, X18. Other parts of its surface more as shown in fig. 5.

9. Vertical section x18.
10and 11. Average tangential section X18 and small portion of same 50.

12.

Transverse section, natural size and one fifth of it X18. Note comparatively small size
of the tubes in the axial region and wide peripheral region.
Upper third of the Trenton shales, St. Paul.

Figs. 13 to 17. CALLOPORA PULCHELLA, Var. PERSIMILIS, D. VAT... .. cece eect tree ere teen cence rece 284

13.

14.

Two fragments showing the exceeding prominence of the monticules.
Portion of the surface between the monticules X18.

15 and 16. Vertical and tangential sections <18.

17. A transverse section, natural size and portion of same 18.
Upper third of the Trenton shales near Cannon Falls,
Figs. 18 to 28. CALLOPORA CRENULATA, D. SD...seeee ce cece cece tees eee cence nee e tees tees tees en ence 284
18, A fragment of the zoarium of this species, natural size.
19. Surface of same x9.
20. Average tangential section X18. Another, representing a more matured condition,
rather closely resembles fig. 10.
21. Vertical section X18.
22. Several tubes from the axial region of same X18, showing the wavy character of the walls.
23. Portion of one of the maculx and adjacent parts of a specimen that preserves the cen-
trally perforated zocecial closures, <18.
Upper third of the Treuton shales, St. Paul.
Figs. 24 to 31. CALLOPORA UNDULATA UIP....... cece cece cece ce nee e tees teeta nee ceseeteteacncecs 279

24 and 25. Typical specimens of the natural size.

26. A fragment with rounded monticules. These are too prominent in the figure.

27. Nearly smooth fragment, in this respect approaching C. incontroversa.

28. Surface of the original of fig. 25, x9.

29. Tangential section x18.

30. Portion of a transverse section x18.

31. Vertical section x18.

Middle third of the Trenton shales, St. Paul and Minneapolis.
Figs. 33 to 36. CALLOPORA INCONTROVERSA UIr.............0.025 cones feisaceinlaseieva.aacailn'g ays Geers bee Sew Ul 278

33. Tangential] section X18, representing part of one of the clusters of large zocecia and a
few of those of the ordinary size. Compared with C. undulata (fig. 29) it will be noticed
that they are of more rounded shape.

34. The central part of a transverse section X18

35. The axial part of a vertical section X18. At the right upper corner one of the tubes is
drawn to its aperture,

36. Anentire but rather short zocecial tube x18, showing the distribution of the diaphragms.

Lower third of the trenton shales, Minneapolis.
Figs. 87 to 41. CALLOPORA ANGULARIS, DSP. i... eee e cece cece cece cee cc ae ce eeenes cece senneeeee. 277

37. Fragment of the natural size.

38. Vertical section x18.

39. Tangential section showing fully matured characters, x18,

40. Small portion of another tangential section <18 showing the slightly irregular character
of the cells at a deeper level in the zoarium than that represented in fig. 39.

41, (14 0n some of the plates.) Axial region of a transverse section X18,

Lower third of the Trenton shales, Minneapolis.
Plate XxI.

 

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Figs. 1t08. CALLOPORA DUMALIS, 1. SP..eceecece cece ce cece cee ee eee te en eee enn ene E EEE EERE EES 28:
lto4. Representative fragments of the natural size.
5. Surface of the slender piece x9.
6. Surface of another that preserves the zocecial closures, x18.
7and 8. Vertical and tangential sections x18.
Upper third of the Trenton shales, St. Paul.

Figs. 9, 10, 21 and 29. CALLOPORA GOODHUENSIS, 1. SP........ cece cece eee e cere eens ee ee nee en tee aees 28%
9and 10. Two fragments of the natural size.
21. Axial region of a transverse section x18.
29. Surface of a specimen x9.
Galena shales near Cannon Falls, Minn.

Figs. 11, 12, 16, 17, 24-26, 30, 31. CALLOPORA MULTITABULATA UIL......ec cece see teeee gener ereenee 28C
1land 12. Montiferous examples, the latter but slightly, from the Galena shales at Cannon
Falls.

16. Typical specimen from the upper third of the Trenton shales at St. Paul.

17. Tangential section X18, of the Galena shales form.

24. Vertical section of a specimen like fig 16, x9.

25. Surface of the original of fig. 16, <9.

26. Surface of a very finely preserved specimen x18, showing the ornamental zocecial
closures. Upper third of the Trenton shales, St. Paul.

30. Surface of a specimen like the one from which the illustrated tangential section (fig 17)
was prepared, X9. The figure includes one of the clusters of large zocecia.

31. Surface of a typical specimen x9.

Figs. 13-15, 18-20, 22, 23, 27,28. CALLOPORA AMPLA, D. SD......-. 0 cece cece cece nce ceceec cee enneneee 28)

13. A large irregular specimen from the Galena shales at Cannon Falls.

14and 15. Two typical examples from the base of the upper third of the Trenton shales
near Fountain, Minn.

18. Tangential section x18, of another specimen from the same horizon and locality as
the preceding.

19. Vertical section of the same x9.

20. The axial region of a transverse section of the same X18.

22 and 23. Portion of one zocecial tube of a vertical section and a tangential section, <18, of
a specimen like figs. 13 and 28. Galena shales, Cannon Falls.

27. Surface of the original of fig. 14, x9.

28. Surface of the original of fig. 13, x9.

Figs. 32 to47. DEKAYELLA PRHZNUNTIA, n. sp., and varieties.
Figs. 32 to 38. War. ECHINATA, 1. Val... .. ccs cee cece cece cence eee eenn eet sbeeencas saeceranteecuens 27:

32. Typical example of this variety.

33 and 34. A less compressed fragment of the natural size and a portion of its surface x9.

35 and 36. Two portions of a tangential section x18.

37. Vertical section of the same specimen x9.

Lower part of the upper third of the Trenton shales near Fountain, Mion.

38. Portion of a tangential section of a specimen from the upper part of the middle third
of the Trenton shales at Minneapolis; x18. Other parts of this section are precisely
as in fig. 36, but in the portion figured the mesopores are larger and more abundant
than usual for this variety. The vertical section of this specimen is indistinguishable
from fig. 37.

Figs. 39 0 42. Var. SIMPLEX, D, Val... ccc. cas csn ses ee cece eeeee senate cus suseesuseteeevteenecucuces 27
39. Tangential section <18, of a specimen with thick walls.
40. Verysmall portion of the superficial region of a vertical section magnified 50 diameters to
show the minute structure of the walls and the method of depositing the diaphragms.
41 and 42. Small portions of two tangential sections X50, the first with walls as in figs. 39
and 40, the second with thinner walls, parts of which are marked transversely.
Lower third of the Trenton shales, Minneapolis.

Fig. 43, The TYPICAL FORM Of the SpecieS......... 06. cee cec ee cscs cece eset eeee ee ccereeanneteuueees 27
An average tangential section x18. Middle third of the Trenton shales at Minneapolis.
Figs. 44 to 47, Var. MULTIPORA, 0. VAL... ... 21. eee cece cece ene ete cent en cee esteneeenecunscnneeeuee 27

44. A tangential section X18, with very thin walls and small acanthopores.
45 and 46. Another tangential section with stronger walls and large acanthopores, x18, and
several cells x50.
47. Vertical section x18.
Middle third of the Trenton shales,Minneapolis.
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Fig. 1 to 4. HEMIPHRAGMA OTTAWENSE (FOOrd)........ccceccec cece ee seen eee cen teeta seseeentn tenes 30!
land 2. Two portions of a tangential section 18, showing differences due to age.
3. Vertical section x9.
4. Small portion of the peripheral region of the same 35.
Upper part of the Galena shales, Mantorville, Minn. Survey Museum, Reg. No. 6002.

Figs. 5 to 19. HEMIPHRAGMA IRRASUM UIL....... lice cee cece ee cee ce teen nee ee cent eb eteeeanes 29!

5. Vertical section x9.

6,7,9and 14. Four tangential sections x18, exhibiting individual variations.

8. Small part of a transverse section X18.

10 to 18. The surfaces of four specimens *9, fig. 10 representing a wood average, fig. 12 the
appearance of young examples, and figs. 11 and 13 the fully matured conditions.

15 to 19. A group of five specimens, three of them of the average size, while 17 is the largest
and 18 one of the smallest seen.

Lower third of the Trenton shales at Minneapolis, and the Galena shales near Cannon

Falls, Minn.

Figs. 20 to 23. HEMIPHRAGMA TENUIMURALE, D, SD... - sees cece eect c eee ence ne eee ttneneeeeseees 30:
20. Vertical section X18.
21 and 22. Tangential sections X18, the first showing the fully matured condition, the
second a younger stage in the development of the zoarium. 7
23. Surface of a well preserved example showing the incomplete diaphragms in the zocecial
cavities, <9.
Galena shales near Cannon Falls.

Figs. 24 to 31. STROMATOTRYPA OVATA, D. SP. eee cece eect cece cence ete teen eee e ete teeeeeteeeneees 30:

24. Surface of an old example 9.

25, Well preserved specimen consisting of several layers, natural size.

26. Small portion of one of the first layers of same X18, showing an aged condition.

27. Part of the last layer of same 18, showing appearance of surface in the youngest stage
observed.

28 and 29. Tangential and vertical sections <18, of an example consisting of three distinct
layers of zocecia

30 and 31, Another pair of sections, vertical and tangential, the latter illustrating a more
aged condition than is shown in fig. 28; X18.

Middle third of the Trentén shales, St. Paul and Minneapolis.
    

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PLATE XXV.

Figs. 1 toll. BATOSTOMA FERTILE UL. .... 0. cece cee ee teen e een e eee beeen eee eee
land 2. A small and a large specimen. :
3. Surface of the larger specimen, which is a typical example of the species, *9.
4. Tangential section, prepared from the same specimen, X18.
5 and 6. Surface of the var. circulare x9 and X18.
7. Tangential section of aspecimen with very thin walls and exceedingly small acantho-
pores, X18, The shaded spaces are mesopores.
8and 9. Tangential sections of two specimens of the var. cireulare, X18, the first with very
thick wall, the second with them thinner and in this respect agreeing with figs. 5and 6..
10. Portion of the axial region of a transverse section of a typical specimen, X18.
11. Vertical section of the natural size and a portion of same 18; typical.
Lower third of the Trenton shales, Minneapolis.

Figs. 12 to 15. BATOSTOMA MAGNOPORA, D.SDP.. eee cece cece eee cette eee cence e eee eens 29
12. A rather small specimen of the natural size.
13. Tangential section X18.
14, Part of the axial region of a transverse section X18.
15. Vertical section x9.
Middle third of the Trenton shales, Minneapolis and St. Paul.

Figs. 16 to 25. BAVOSTOMA VARIUD, De SD. sess cuncdssecda coseceas swetee@aee seve vedas eeeada ces ceed 29

16 to 22. Seven figures illustrating the extreme variability displayed by tangential sections
of this species; x18. Figs. 16 and 17 represent different parts of the same section, 18
shows the tubes just after bending out of the axial region, 16, 19 and 20 are of common
occurrence, and 21 and 22 show extremes rarely met with.

23 and 24. Halves of two vertical sections x9, the first normal, the second indicating some
disturbance in the development of the tubes.

25. One zoccial tube of a vertical section of the basal expansion X18.

Middle third of the Trenton shales at St. Paul and Minneapolis.

Figs. 26 to 28. BATOSTOMA MONTUOSUM, D. SP....0..0ccccceccce cece vues cece teeueteeneceaeceenteuees 29
26. An average specimen of the natural size.
27 and 2€. Surface of a specimen with numerous closed mesopores <9 and a small portion of
same X18. In many specimens the interspaces are narrower than is shown in these
figures.
Upper third of the Trenton shales near Cannon Falls, Minnesota.

Figs. 29 to 36. BATOSTOMA HUMILE, 0. SP.........e eee eeeeee CERAA MONET ced ea barney amamonineeeainms 29
29 to 31. Three fragments of the natural size.
32. Small portion of a tangential section 18, of a specimen having a surface like fig. 34.
33. Tangential section of a less matured example 18.
34. Surface of an average fully matured example x9.
35. Surface of a young example (corresponds to the lower part of fig. 33) X18.
36. Surface of a fragment regarded as illustating a condition of extreme age, X18.
Galena shales near Cannon’Falls, Minn.
ate XXV

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PLATE XXVI.

Figs. 1 to 6. BYTHOPORA HERRICKI UIr ....... cece eee nee entree ene nena en renee eres 26:
1. Vertical section 18, showing slight irregularity in the gtowth.
2and 3. Tangential section X18 and a portion of same 50. ‘
4and 5. <A large and an average sized specimen.
6. Surface of the smaller x9.
Middle third of the Trenton shales at Minneapolis.

Figs. 7109. BYTHOPORA ALCICORNIS, 1. SP... ce. cece cece eee een eee eee n nee seen eter ene ennenees 26:
Tand 8 ‘Two specimens of the natural size.
9. Surface of the larger one x9.
Upper third of the Trenton shales near Cannon Falls.

Figs.10 to 16. HoMOTRYPELLA (?) SUBGRACIUIS, ND. SD.. ss sec ee eee eee teen eee eee nent ene et eneees 231
10and 11. Two tangential sections X18, showing slight differences.
12, Vertical section X18... The structure is almost entirely destroyed and only the direc-
tion of the tubes is to be made out with any certainty.
13 and 14. Two specimens, the second a little above the average in size.
15 and 16. Surface of the larger specimen <9 and x18.
Middle third of the Trenton shales, St. Paul.

Figs. 17 to 19. ERIDOTRYPA EXIGUA, D.SP.... ee eect cee een ete teen nee ene nnn e eee eees 26
‘17. A group of fragments as they appear mounted on a slide.
18 and 19. Twoof them x9.
Upper part of the Galena shales near Cannon Falls.

Figs. 20, 21, 29 and 30. ERImDpoTRYPA MUTABILIS, Var. MINOR, D. Var... . sss e cece cece cece eee er aeeees 26
20. Three fragments of the natural size.
23. Surface of one of them *9.
29 and 39. Vertical and tangential sections x18.
Galena shales near Cannon Falls.

Figs. 22 to 28, 31,32. ERIDOTRYPA MUTABILIS, ND. SD... .. cs cece cece eee eee nee e ener eee t een eenees 26

22. A specimen of the average size.

23. Large example.

24. Surface of an old example presenting an unusual appearance, X18.

25. Surface of the original of fig. 23, x18. The figure includes one of the macule and ex-
hibits the most common appearance of these.

26 and 27. Tangential section X18 and a portion of same <50; represents an average fully
matured condition.

28. Vertical section of the same specimen X18; shows a superficial layer of zocecia growing
in a direction opposite to the first set.

31 and 32. Vertical and tangential sections X18, of am old specimen which has grown irreg-
ularly causing many interspaces and thus unusually numerous and large mesopores.

Galena shales, Goodhue county, Minn. :

Figs 33 to 37. BATOSTOMA WINCHELLI UlP......... cece ce cence cece ene tenn ee eee eeee essen eneneneee 2
33. A specimen of the usual diameter.
34. Another, of large though not uncommon size.
35. An average example of the var. nodosa.
36. Surface of a fully matured example x9,
37. Surface of the original of fig. 33 x9 and X18. (See also plate 27.)
Middle third of the Trenton shales, Minneapolis and St. Paul.

Figs. 38 to 40, BATOSTOMA MINNESOTENSE, 1. SP..... 00.00. ccceccccceeeeecuureuueeees ieee dates 12
33 and 39. Two specimens, the first small, the other of the average size.
40. Surface of the larger specimen, which is in an excellent state of preservation, <9, show-
ing the granulose walls. (See also plate 27.)
Middle third of the Trenton shales, Minneapolis.
 

Plate 26.

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MACBRAIR LiTH.Co. Cin.
PLATE XXVIL.
PAGE

Figs. 1 to 8. BATOSTOMA WINCHELLI UlIr...... 0. eee c cee eee eee teen enna rere reese 29:
1,2and 3. Vertical sections X18, of a young, medium, and an old specimen.
4and 5. Tangential section, X18 and X50, of the same specimen from which was prepared
the vertical section shown in fig. 3.
6. Tangential section of a young specimen 18.
7and8. Tangential section of the var spinulosum X18 and x50. (See also plate 26.
Middle third of the Trenton shales, Minneapolis and St. Paul. :
Figs. 9 to 15. BATOSTOMA MINNESOTENSE, D. SP....--eeeesece cere ee cee eee eeree’ Suid neds eaaeweey 29"
9andi0. Portions of a tangential section 18 and X50.
11 and 12. Peripheral and axial regions of a vertical section prepared from the same speci-
men as the preceding, 18.
13. The peripheral part of a zoccial tube with fewer diaphragms than usual, x18. The true
average for the species is intermediate between this and fig. 11.
14.and 15. Portiotis of two tangential sections, X18 and X50, in a different state of preser-
vation than figs. 9 and 10. (See also plate 26.)
Middle third of the Trenton shales, St. Paul and Minneapolis.

Figs. 16 to 19. BATOSTOMA (?) DECIPIENS, 1. SP... ccc c cece cece eet ete eee en teen teen enn enenes 295
16. Small portion of a vertical section x18.
l7and 18. Tangential section x18 and x50. In some parts of this section certain small
acanthopore-like dots are distinguishable usually about midway between the angles.
They are dark and scarcely half the size of the smallest shown in fig. 10.
19. From the axial region of a transverse section X18.
Lower half of the Trenton shales, Minneapolis.

Figs. 20 and 21. LEPTOTRYPA CLAVIFORMIS, D. SP......c cc cee cece cece cee cnet e teen ee eneeeeeeeeee 31!
20. Tangential section X18. In this section the cells here drawn as open are filled with
matrix, while those shaded are occupied by clear calcite. The smaller of the latter
have the appearance of mesopores; on the other hand, since the preservation of the
7 fossil is not favorable, it is possible that they represent acanthopores.
21. Vertical section of the upper extremity of same beyond the foreign body, X18.
Middle third of the Trenton shales, St. Paul.

Figs. 22 and 23. LEPTOTRYPA INFORMIS, D.SD.... cc esc e cece eee tees ete teen e eee eee e eens Hiawedne BI
Tangential and vertical sections X18. .
Lower third of the Trenton shales, Minneapolis.

Figs. 24and 25. LEPTOTRYPA ACERVULOSA, D.SD..... ccc c eee c eee ee ee eee eee tee ee ne ee eens 31.
Tangential and vertical sections x18.
Galena shales, Decorah, Iowa.

Figs. 26 and 27. MoNoTRYPA (?CHAETETES) CUMULATA, D. SDP. .-. see e cece ee cence erent neeeeteeaenes 30
Tangential and vertical sections x9. Beneath the first the stricture of the wall is shown X35.
Upper part of the Galena shales, Goodhue county, Minn.

Figs. 28 and 29. MONOTRYPA MAGNA, D. SD... cece cece cece cece cece tee eee ntteeseeanee megahaete te 30
Vertical and tangential sections <9.
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PLATE XXVIII.

Figs. land 2. SPATIOPORA LABECULOSA, 1. SP. ..ss cece ce eee ee teen eee nee tenn nee ne ee teen tnenas
1. Surface, <9, of a specimen with macule of the usual size. Others may have smaller
macule and more numerous mesopores between the zocecia.
2. Tangential section of same, X18.
Middle third of the Trenton shales, Minneapolis, Minn.

Figs. 3 to 7. CERAMOPHYLLA FRONDOSA, D. GeN. Cb SP.... see ee cece ee cece ee ee cee eens sete eeanee
3. Nearly complete frond of this species, nat. size.
4. Small portion of its surface, x9, showing in the lower left hand corner the greater part
of one of the macule. ‘
5and6. Small parts of two tangential sections, X18, the former illustrating the normal
development, the latter an old and more irregular arrangement, and greater width
of interspaces due to proximity to a macula.
7. Half of a vertical section, X18; the tubes are divided somewhat obliquely and therefore do
not show the full length of the prostrate portion.
Upper third of the Trenton shales, St. Paul, Minn.

Figs. 8 to 11. CERAMOPORELLA INCLUSA, DL. SP..... 0... eee ee cee ene ween eens sal) Ae epee tas
8. Surface, x9, of an example having the apertures filled with the clayey matrix.
9. Small portion of another example, x18.
10. Larger part of the surface of the original of fig. 9, <9.
11. Selected normally developed zocecium, 40.
Lower and middle thirds of the Trenton shales, Minneapolis, Minn.

Fig. 12. CERAMOPORELLA INTERPOROSA, D. SP.... ee se cece cece ee cee cece eee ne tee euetteeneeen vs
Surface of an average specimen of this species <18.
Galena Shales near Cannon Falls, Minn.

Fig. 18. CERAMOPORELLA DISTINCTA, UIl......... 000. (cacescccecneeeeeeeeteeteeeeeeeeeeeccrec :
Surface of a small specimen of this species from the lower third of the Trenton shales

at Minneapolis; x18.

Fig. 14. DIAMESOPORA TRENTONENSIS, 1. SP... . 6. eee cece cece e cece cece eee ceancseusuucesoeee
Two specimens of the natural size and the surface of the upper x9. The form and ar-

rangement of the zocecia is a little irregular in this specimen. In others their shape

approximates fig. 11.
Galena shales near Cannon Falls, Minn.

Figs. 15 to 20. ANOLOTICHIA IMPOLITA UIP... . ccc cece cece cece nce eee n eee cee seen neeeutenes
15and 16. Surface x9 and x18.
17. From the axial region of a transverse section X18. .
18. Small portion of a tangential section X18, of a specimen in which many of the lunaria
have only two tubuli.
19. Portion of a typical section x18.
20. Vertical section <9. .
Lower third of the Trenton shales, St. Paul and Minneapolis.

Figs. 21 to 25. BYTHOTRYPA LAXATA UIL........ 0... eee ccc cece cc nn erence eee eens eeeccees

23 and 24. Vertical and tangential sections x9.
25. Portion of the tangential section x18.
Trenton shales, Minneapolis and St. Paul.

Figs. 26 to 28. CREPIPORA SUBHQUATA, N. SD.... cee cece cece cece eee cee een cenenecs
26and27. Tangentialsection x9and X18. 0s
28. Vertical section <9, the entire thickness of the zoarium being shown in the right half
of the figure.
Upper third of the Trenton shales, St. Paul.

Figs. 29 to 82. CREPIPORA PERAMPLA, I. SD.... ee sees ccceee cece cece ee ccneceuneneencees
29and 30. Vertical and tangential sections <9, the latter with the lunaria unusually distinct.
31. Portion of the tangential section x18.
32. Another tangential section <9, with the lunaria scarcely distinguishable.
Top of the Trenton limestone, Fillmore county, Minn.

329

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