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lEztraeted from the Geolooioal Magazine, Decade IV, Vol. IV,
No. 892, p. 68, February, 1897.]

The Oldest SiPBoyoTHiSTd.

By G. F. Matthew, D.Sc, I .il.S.C.

(Read before the Natural History Society of New Brunswick, January 6, 1897.)

niHE ancient Brachiopodous genus Siphonotreta is well known
X by Its species occurring in the Ordovician and Silurian strata
ot Kussia and Great Britain, and its peculiar pedicle opening has
been the subject of remark. The author is not aware that this
genus has hitherto been reported from any Cambrian terrain, and
therefore, the greatest interest will attach to a form recently found
in the lower beds of the St. John Group, which is nearer to Siphono-
treta than to any other known genus.

The new form is remarkable, so far as its pedicle passajre is con-
cerned, m corabming the two genera Siphonotreta and Schizambon :
fcr in Its early stages it had the dorsal furrow of the latter genus
but afterwards it developed the tubular passage seen in the former.

Ihis shell 18 older than any Paradoxtdes, being of the Protolenua
±auna, and is found in strata that nearly correspond in age to the
beds wh«ch at another locality carry tlie related genus Trematobolua.
But while the new form abandoned the Schizambonal opening for
Its pedicle, and adopted a contracted canal for the passage ot" this
organ similar to that of Siphonotreta, Trematobolus maintained the
open fissure (or hole) through life.

Young individuals of the new form of the size of Schizambon
typ*calt8 Waloott, are actual examples of the genus Schizambon.
Ihe history of the growth of the species from the larval forms to
maturity is shown by exfoliated shells, in which the siphon stands

' Trans. New York Acad. Sci., vol. xir, pp. 101-153.

'TT-

Dr. O. F. Matthew— The Oldest Siphonotieta.

out, while the adjoining shell-layers are weathered away. The shell
of this species was thin during the Sohizambonal stage, but thickened
rapidly by the accretion of layers within the shell during the Sipho-
notretal stage. As, however, the parts of these layers around the
tube were not perfectly calcified, that organ in exfoliated shells
stands out and remains as a projecting tube, after the layers of shell,
as above remarked, are weathered away.

In an exfoliated shell, therefore, we have a siphon projecting from
what seems to be the inner side of the shell, and simulating the
figures given of the interior of the ventral valve of Siphonotreta
unguieulata, Eiohwald.' And the resemblance to that species in
other respects is significant, for, in the first place, the passage for
the pedicle in the new form diminishes in size from that which it
had at the close of the Schizambonal stage, until maturity ; and it
will be noted that in the species of Siphonotreta named above, it is
said that the internal tube diminishes in size as it passes inward.'

It is also stated that in Siphonotreta unguieulata the muscle-marks
are very near the internal opening of the tube. This is not notice-
ably the case with the new form when the interior of the shell is
completely preserved ; but in exfoliated examples where the siphonal
tube is exposed, the musnle-markings on the shell-layers remaining,
being those of the early Siphonotretal condition, are much nearer the
siphon, and so are like those accredited to the species ibove nam ad.
The new form has no exsert siphon showing on the inner surface
of the shell, and it will easily be seen that such a projecting tube
would involve anatomical conditions different from those of most of
the early Neotrematous Brachiopoda. It would appear that a siphon
projecti!)g inside the shell is not an invariable characteristic of
Siphonotreta, for Davidson figures 8. unguieulata with a scarcely
projecting siphon,* and De Verneuil shows the inside of an umbo of
S. verrucosa, De V., in which the opening for the pedicle lies in
a little saucer-shaped hollow, as in our species.*

In some species referred to Siphonotreta, the pedicle passage opens
outward just behind the beak ; in others a channel extends along the
back of the shell for some distance, and then a hole gives passage to
the interior of the shell, there being no siphon or tube, ""'lese latter
have been divided off by Walcott as the genus Schizau ,/i. Since,
however, the St. John species agrees exactly neither with this section
nor the other, but in its pedicle passage combines the characters of
both, it is necessary to establish for it a separate place. Linking
together as it does the genera of De Verneuil and Walcott, it would
seem proper to regard both Schizambon and the new form as sub-
genera of Siphonotreta, and with this view the author would propose
for the now form the name Protosiphon, for which the above
remarks will give the essential characters.

> See " Manual of the Mollusca," S. P. "Woodward, London, 1875, p. 390,

"« Hall and Clarke, " Genera of PaliBozoic Brachiopoda," Albany, 1892, P- HO.
' Gbol. Mag., London, 1877, PI. II, Figs. 9, 11. See also Hall and Clarke,
" Genera of Palneozoic Brachiopoda," pi. iv, fig. 25.
* '' Russia and the Ural Mountains,'' Paris, 1846, vol. ii, pi. i, fig. H<».

MUM

Dr. O. F. Matthew— The Oldest Siphonotreta. 70

PROTOSIPHON, n. subgen.
Pkotosiphon Esmpandm, n.Bp.' '

^ I

ProtoBiphon Aempanum.—l. Interior of the ventral ralve, showing scars of central
and lateral muscles, opening of the siphon, vascular trunks, etc. 2. Interior of the
dorsal valve, showing position oL the central and lateral muscles, median ridpe
vascular trunks, etc. 3. Section of the beak of the ventral valve, showing the
passage for the pedicle. 4. Umbo of the ventral valve viewed from above, showing
tho Schizambonal furrow.— All the figures are magnified f , except No. 3, which is
enlarged f .— N.B. The large figures are somewhat idealized, as some features (e.g.
the vascular trunks) are supplied from examples other than the two which formed the
basis of these drawings.

Shell substance caloareo-corneous. Outline of the dorsal valve
somewhat oblately orbicular ; outline of the ventral valve similar,
but with an obtusely pointed beak. Both valves moderately convex!
and marked at the hinge area by transverse ridges of growth. The
ventral valve has a depressed channel on the back, beginning at the
beak and ending forward in a tube buried in the substance of the
shell, and terminating inwardly in the visceral cavity by a minuto
opening.

The dorsal valve does not differ much from the ventral, except in
the absence of a projecting beak, and in being more tumid in tho
posterior half. Both valves have a broad, shallow sinus towards
the front, and so are there straighter than in other parts of their
circumference.

The edges of both valves are flattened on the underside, and
thickened at the cardinal line, where they are traversed by arched
ridges and furrows, which may serve the purpose of articulation.
A depression similar to a pedicle groove traverses the cardinal area
of the ventral valve on the axial line ; and a low tubercle holds
a similar position on the dorsal valve.

Sculpture.— The surface of the shell is marked by fine lines,
concentric to the umbo, and at intervals by stronger growth-lines.

\ Dedicated to Dr. J. F. Kemp, Professor of Geology at Columbia College
University, New York, well known for his work on the Archsean and Cambrian
Geology of the State of New York.

r:'

■u.- i mu.. ■ ^ W ' Vi'.. ?.M ' ! ' y" "■ I ". ' .ij . l y

■5^

Dr. O. F. Matthew— The Oldest Siphonotreia.

Interrupted rowi of tubercles appear in certain places along these
lines of growth.

Sim.-— The largest dorsal observed was 19 mm. long and 20 mm.
wide. A ventral valve of corresponding size would be 1 mm. longer.
Height of each valve about 6 mm.

Horizon and Locality. —In the olive-grey sandstones of Division 16
of the St. John Group at Long Island in Kennebecasis Bay, King's
County, N. B. Canada. The exact horizon in Band b is uncertain :
there are about fifty feet in thickness of these sandstones exposed,
and they have the aspect of Assises 2 to 4 ; being from the upper
part of the sandstones the species is probably from Assise 8 or
Assise 4, These shells are found sparsely distributed in sporadic,
lenticular layers, having the valves promiscuously packed within
each other, as though after death they had been somewhat rolled
on a beach, or in a shallow sea.

Further particulars of this species will be given in an article
in p-jeparation for the Royal Society of Canada.

these

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