s 14. GS: CIR 247 GxtA SkjSlQ'u^ STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS, Director Chitinozoan Faunule of the Devonian Cedar Valley Formation Charles Collinson Alan J. Scott DIVISION OF THE ILLINOIS STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA CIRCULAR 247 ILLINOIS GEOLOGICAL SURVEY LIBRARY JAN 30 1958 1958 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00004 4531 CHITINOZOAN FAUNULE OF THE DEVONIAN CEDAR VALLEY FORMATION Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/chitinozoanfaunu247coll CONTENTS Page Introduction 5 Laboratory techniques 6 Stratigraphic and geographic occurrence 6 Faunal summary 7 Comparison with related faunas 9 Associated fauna 10 Systematic paleontology 11 Genus Angochitina Eisenack, 1931 11 Genus Ancyrochitina Eisenack, 195? 18 Genus Sphaerochitina Eisenack, 1955 20 Genus Earlachitina n. gen., n. sp 25 References 34 Table 1. - Measurements of type specimens 22 ILLUSTRATIONS Plates 1, 2, and 3- - Cedar Valley chitinozoan faunule . Text figures 1. - Stratigraphic section at Milan quarry . . 2. - Diagrams illustrating application of ratios 3- - Angochitina milanensis n. sp., characteristic shape and variant 4. - Angochitina devonica Eisenack. 5. - Angochitina cf. A. devonica Eisenack 6. - Angochitina globosa n. sp. . . 7. - Angochitina mourai Lange . . . 8. - Ancyrochitina cornigera n. sp. 9. - Ancyrochitina megastyla n. sp. 10. - Sphaerochitina pilosa n. sp. 11. - Sphaerochitina schwalbi n. sp. 12. - Sphaerochitina nodulosa n. sp., and S. cf. S. nodulosa 13- - Earlachitina latipes n. gen., n. sp Page 29, 31, 33 8 12 13 14 15 16 17 19 20 21 23 24 26 CHITINOZOAN FAUNULE OF THE DEVONIAN CEDAR VALLEY FORMATION Charles Collinson and Alan J. Scott ABSTRACT The Chitinozoan faunule of the upper Middle Devonian Cedar Valley formation from a single outcrop in northwestern Illinois is described. The faunule, which is abundant and diversified, repre- sents more than thirteen species referable to four genera. One new genus, Earlachitina, and eight new species are described and named. The faunule is distinct from the previously described Devonian Clear Creek, Bailey, and Grand Tower faunules of Illinois and Indi- ana, but has elements in common with Devonian faunules from Brazil and Germany. The technique of collecting and preparing chitinozoan speci- mens from limestone is discussed. INTRODUCTION In 1955, as part of a summary of the distribution of Chitinozoa, Collinson and Schwalb listed 2 occurrences of these microfossils in North America. Among them were three distinct faunules of Devonian age - one from the Clear Creek formation as represented in samples from a number of wells in the Illinois basin, another from the Bailey formation in southern Illinois and western Indiana, and a third from the Grand Tower formation in both eastern and western Illinois. Shortly after the Collinson and Schwalb (1955) report was published, a fourth Devonian chitinozoan faunule was discovered in the Cedar Valley limestone in north- western Illinois. This faunule, which is remarkably abundant and diversified, repre- sents the youngest known occurrence of chitinozoans. In general aspect, it is quite different from other Devonian faunules and contains important elements never before described. The Cedar Valley faunule therefore is of special interest for it seems to indi- cate that chitinozoan species evolved rapidly enough to make them useful for detailed zonation whenever adequate data are assembled. That chitinozoan species have con- siderable lateral distribution independent of facies changes has already been established by study of the Clear Creek faunule. The great numbers encountered in the Cedar Valley faunule and the ease in collecting and processing them also lends encouragement for their stratigraphic use. Because the Cedar Valley chitinozoans are variable both in form and preser- vation, we have illustrated as many examples as possible (pis. 1-3)- Lest this be confusing, we have also included text figures showing our interpretation of an average representative of many species. The plate illustrations are camera lucida (5) 6 ILLINOIS STATE GEOLOGICAL SURVEY drawings made in pencil on coquille drawing board by the authors. Most of the stippled text figures were made by Marie Litterer. Howard Schwalb did much of the processing and mounting of samples and Romayne Skartvedt made invaluable trans- lations of foreign literature. For their help we are indeed grateful. The terminology used in this report is that of Collinson and Schwalb (1955, text fig. 4) although we have also adopted use of the term "apical angle" (Offnungs- winkel) as applied by Eisenack (1955a, p. 163) to the imaginary vertex angle of subconical body chambers as found in such genera as Sphaerochitina and Ancyrochitina (text fig. 8). We have further found the application of such ratios as "neck length/over-all length" and "maximum diameter/over-all length" useful in de- scribing some species. Determination of these ratios is clarified in text fig. 2. LABORATORY TECHNIQUES The procedure used to prepare chitinozoans for study is sufficiently different from methods employed in research on foraminifera, ostracodes, and conodonts that a summary of technique merits description here. Because the matrix of the Cedar Valley is an argillaceous limestone and chitinozoans are insoluble in all the well known acids (HC1, HF, and acetic acid), the samples were first crushed and dissolved in acid. The first few samples were dissolved in 20 percent hydrochloric acid but a well preserved conodont faunule was discovered and the remainder of the samples were dissolved in 10 percent acetic acid, so that conodonts could be recovered along with the chitinozoans. Because chitinozoans are quite small (0.1 to 0.5 mm. long) and bear delicate structures such as spines and collars , the insoluble residues were not sieved. In- stead, in order to concentrate the specimens and eliminate much of the clay-sized material, a thin suspension was made of the insolubles in water, and the suspension was poured into Petri dishes to settle. The chitinozoans settle much more rapidly than the clay and after 30 seconds the clay suspension was decanted, leaving a thin layer of coarser material rich in chitinozoans in the bottom of the dish. Water was then added and the chitinozoans picked from the bottom with the aid of a finely drawn glass pipette. Specimens were placed on microslides by blowing gently on the open end of the pipette. In this manner the specimens are kept in water suspension until after they are placed on the slide so that the most fragile specimens may be casually moved without breakage. Upon drying, the specimens adhere to the slide without use of cement and are cemented only after they have been studied and illustrated. STRATIGRAPHIC AND GEOGRAPHIC OCCURRENCE The Cedar Valley faunule was discovered during a systematic search for chitinozoans. A series of 500- to 1000-gram composite samples (text fig. l)were collected from the Milan stone quarry, about half a mile southeast of Milan in north- western Illinois. The site is near the southeastern edge of the Devonian outcrop CEDAR VALLEY CHITINOZOAN FAUNULE 7 belt which extends nearly across the state of Iowa in a northeastward direction and continues only a short distance into northwestern Illinois. Both the Cedar Valley and Wapsipinicon formations are well exposed, but sampling revealed that chitinozoans are restricted to the Cedar Valley. The speci- mens were obtained from a fossiliferous, gray to greenish-gray, fine-grained, argil- laceous limestone representing the middle part of the Solon member of the Cedar Valley formation. Text fig. 1 illustrates stratigraphic distribution of the chitinozoans. The microfossils were common in samples 7 and 8 and were abundant in samples 3 through 6. Species in the faunule are not uniformly distributed throughout the section. With the exception of Angochitina n. sp., which occurs only in bed five, all species, most in their greatest numbers, are present in bed three. In beds four through eight, as well as three, Angochitina milanensis, Angochitina devonica, and Angochitina mourai occur abundantly, but representatives of most other species become less numerous as one goes down in the section. Most do not occur below bed six. Ancyrochitina cornigera and Sphaerochitina nodulosa occur only in bed three but both in considerable numbers. A number of other geographic occurrences of this faunule must be studied before we will know whether the distribution of these species within the zone of occurrence has any stratigraphic significance. FAUNAL SUMMARY The science of describing and interpreting Devonian chitinozoans is barely in infancy so it is not surprising that each new stratigraphic occurrence produces new and previously unknown forms. For example, of the four genera found in the Cedar Valley, one is new; and of the fourteen or more species in the faunule, only two have been described. The species found in the Cedar Valley are as follows: Angochitina globosa n. sp. A. milanensis n. sp. A. devonica Eisenack A. cf. A. devonica Eisenack A. mourai Lan^e A. n. sp. Ancyrochitina cornigera n. sp. A. me gas ty la n. sp. Sphaerochitina pilosa n. sp. S. schivalbi n. sp. S. nodulosa n. sp. S. cf. S. nodulosa n. sp. Earlachitina latipes, n. gen., n. sp. E. spp. Of the above species, three, Angochitina milanensis, A. devonica, and Sphaerochitina pilosa occur in great numbers and can be found consistently even in small samples. Less abundant, but nevertheless common, are such species as ILLINOIS STATE GEOLOGICAL SURVEY PEN1MSYL- VANIAN /M O < Z CL z CO o en > a) UJ - Q 5 UJQ cr = OH *! < o gu. / TTr= \\ 'iL / ^4^ pT^> / ~-% -1 / z < z o > LU o UJ _) O Q o or o u. > UJ _J _) < o UJ o A tr CO 5 B T 1 Z o _J o en 1 r: i \ 1 \ 1 1 z o 1- < q: o u. z o o CL CO Q. < a ^0° c ^5 1 1 o "3 UJ CD 1 UJ rr o z X^ 1 LU > < Q ,1 5 ^oj^o = b|00 ■'■■!' I'\ 1 1 1 1 III \ \ I'll III 1 ' , ' ,\ I I 1 \\ Shale, black, fissile Shale, greenish-gray Limestone, buff, cnnoidal Limestone, greenish-gray, argilloceous, very fossiliferous, ond shale, greenish-gray, very fossihferous Limestone, gray to greenish-groy, fine-grained, very argillaceous, fossiliferous Limestone, groy to greenish -gray, fine-groined to subhthographic, prominent obligue jointing, develops numerous partings where weathered, very fossiliferous 5 feet Limestone, gray, hard, argilloceous, indistinct bedding, fossiliferous Limestone, light gray, brecciated, fragments of corol Limestone, dark gray, subhthographic Limestone, very light gray, lithographic, brecciated Limestone, gray, subhthographic, very hard, much fractured on weathered surface Limestone, very light groy, lithographic Limestone, gray to light gray, stylolific, brecciated in lower part 1 2 3 4 5 6 7 8 * Ed (N 00 • * rj •* 1— 1 ~H (N (N -H ^H -«r i-H JL "* -* 4 c (N i—( (N n CM a Dimensions ^\^^ a. a. a a, a a, d, a. a a. V 00 00 00 oo 00 00 00 00 00 00 S Over-all length .140 .163 .222 .172 .213 .168 .163 .159 .168 .163 .178 Body chamber length .127 .118 .145 .109 .136 .118 .109 .095 .109 .104 .117 Neck length (w. collar) .063 .045 .077 .063 .077 .050 .054 .054 .063 .054 .060 Collar length .009 -- .018 - .022 .013 .013 .009 .009 .009 .014 Maximum spine length .036 .022 .031 .013 « .013 .018 .022 .020 .027 .022 Body chamber width .118 .090 .109 .090 .100 .077 .100 .100 .100 .086 .097 Neck width (average) .050 .045 .045 .036 .054 .036 .045 .050 .045 .036 .044 neck length .33 .28 .36 .37 .36 .30 .30 .34 .37 .30 .33 over-all length * = holotype, * = paratype, -- = : not measura ble. CEDAR VALLEY CHITINOZOAN FAUNULE 13 Fig. 3 - Diagrammatic representations of Angochitina milanensis n. sp. (A) Specimen showing characteristic shape and spine combination. (B) Variant showing unusual number of broad-based spines and indistinct neck, both X250. Derivation of name. - Named for Milan, Illinois. Occurrence. - Common in beds three through eight, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P14-23 (holotype), 8P14a, 8P24-1, 8P13-3, 8P12-32, 8P25-30, 8P2-25, 8P6, 8P1-22 (all paratypes). ANGOCHITINA DEVONICA Eisenack Plate 1, figures 6, 9, 10, 14, 18, 20, 21, 24: Plate 3, figures 22, 26 Angochitina devonica EISENACK, 1955, Senckenbergiana lethaea, band 36, p. 313, pi. 1, figs. 10-12. Translation of original description: - Lower part LneckJ nearly cy- lindrical about one-half to two-fifths of the total length, provided with scarce and usually unbranched, occasionally very long spines; upper part Lbody chamber J flask-shaped, possessing more or less numerous, simple to well branched, partly antler-like and often very bizarrely formed spines, which can be disproportionately broad at the base. The mouth is evenly truncated, yet nearby spines may extend beyond it. Remarks. - Specimens referable to this species are common in almost all samples of the Cedar Valley limestone examined in this study. Considerable vari- ation in shape was noted (text fig. 4), ranging from forms with fairly distinct necks (such as in the holotype) to individuals (for example, pi. 1, fig. 24) that have very indistinct necks. The ratio of length of neck to over-all length of specimen ranges 14 ILLINOIS STATE GEOLOGICAL SURVEY from 0.40 to more than 0.46 so it falls within the limits defined by Eisenack. The average over-all length of our specimens is about 0.200 mm. with the smallest measuring 0.163 mm., whereas the holotype measures only 0.146 mm. and Eisenack's largest paratype 0.152 mm.in length. Although there is more than a ten percent difference between our smallest measured specimen and the holotype, we feel that the similarity in shape and proportion greatly outweighs the difference in size. Angochitina devonica is similar to Angochitina bifurcata Collins on and Schwalb, the latter having a much longer collar and finer narrow-based bifurcate spines and lacking the broad-based, very irregularly branched spines that are so characteristic of devonica. The number and relative density of spines is quite variable in dev onica, and specimens almost completely covered with spines (pi. 1, fig. 24) as well as those bearing relatively few spines (pi. 1, fig. 14) have been re- ferred to this species. The relationship of devonica to milanensis has already been discussed in detail. Fig. 4 Angochitina devonica Eisenack. (A) Common body form bearing characteristic spine combi- nation. (B) Large elongate variant with tapered neck. This form is relatively common in our collections. Doth X250. Measurements. - The following table shows dimensions in millimeters of nine well preserved specimens chosen at random, plus two representative figured specimens. Measurements were made with a micrometer ocular. ^-^ Specimen no. o CD a rr, » a (N (N * * Dimensions ^\. a, 00 00 00 0, 00 Oh 00 00 00 00 00 00 a, 00 c 2 Over-all length .254 .181 .209 .209 .218 .190 .190 .163 .181 .200 .204 .200 Body chamber length .136 .109 .109 .118 .127 .109 .109 .090 .109 .118 .122 .114 Neck length (w. collar) .118 .072 .100 .090 .090 .081 .081 .072 .072 .081 .080 .085 Collar length .022 .027 .018 .015 .018 .018 .018 .009 .013 ~ .022 .018 Maximum spine length .022 .018 .013 .018 .031 .036 ~ .027 .009 .018 .022 .021 Body chamber width .127 .090 .095 .104 .109 .109 .090 .077 .081 .100 .090 .097 Neck width (average) .063 .040 .036 .045 .054 .045 .045 .045 .040 .045 .050 .046 neck length .46 .40 .48 .43 .42 .43 .43 .44 .40 .43 .40 .43 over-all length figured specimens, -- - not measurable. CEDAR VALLEY CHITINOZOAN FAUNULE 15 Occurrence. - Common in beds three through eight, Solon member, Cedar Valley formation, near Milan, Illinois. Also reported from the lower Middle Devonian, Lower Rommersheimer beds ("Lepidocentrus marl") of the Gerolstein basin in the province of Rheinland Pfalz, western Germany. Repository. - Illinois State Geological Survey, 8P7a, 8P25-12, 8P1-2, 8P11-48, 8P2-26, 8P18-5, 8P1-44, 8Pll-21a, 8P11-10, 8P10-43, 8P57-5, as well as specimens listed in table of measurements. ANGOCHITINA cf. A. DEVONICA Eisenack Plate 1, figures 15, 17 Several specimens in our collections are fairly close to Angochitina devonica Eisenack but are more slender and tapered (text fig. 5). Most possess scattered simple spines or spine bases, have indistinct necks, and appear to lack collars. Preservation is in general rather poor. The largest diameter is very near the aboral end, tapering to the mouth without interuption. This shape is very similar to that of the genus Conochitina. Occurrence. - Uncommon in beds three and five, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P2-26, 8P18-5, (figured specimens). ANGOCHITINA GLOBOSA, Collinson and Scott, n. sp. Plate 1, figures 11, 13, 22, 23, 25 Fig. 5 - Angochitina cf. A. devonica Eisenack. Tapered form with indistinct neck, X200. Angochitina globosa is characterized by a globular body chamber with relatively long bifurcate spines and a neck of variable length terminated by a short collar (text fig. 6). The ratio of length of neck, including collar, to over-all length ranges from 0.31 to 0.43. The spines ornamenting the surface of the test are predominantly coarse, relatively long, (up to l/5 of the test diameter) and bifurcate, but a mixture of both short and long spines is generally present. Remarks. - Angochitina globosa is closely related to Angochitina mourai Lange, differing only in its larger size, slightly shorter neck, and possession of long, coarse, bifurcate spines rather than the numerous, fine, simple spines of the latter. A. globosa is variable so that a few specimens approach the shape of some variants of Angochitina milanensis. Angochitina echinata, the type species of the genus, is similar to globosa, but echinata has a much longer neck and unbranched spines. 16 ILLINOIS STATE GEOLOGICAL SURVEY Measurements. - The following measurements made with a micrometer ocular represent dimensions in millimeters of well preserved specimens chosen at random. ^\. Specimen no. cm • r-~ o >o • v\ (N - 1 (N C\ (N m -.i:*- :»■ ■ .:&&■ v. • ? Derivation of name. - From Latin corniger meaning "horned." Occurrence. - Common in bed three, Solon member, Cedar Valley for- mation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P16-2 (holotype), 8P1-21, 8P22-5, 8P18-8, 8P22-4, 8P16-23, 8P16-5 (paratypes). ANCYROCHITINA MEGASTYLA Collinson and Scott, n. sp. Plate 2, figures 1-3, 7 Although not common, this species Fig. 8 - Diagrammatic representation of is distinctive and easily identifiable. It is characterized by a subconical body chamber and a long cylindrical neck. The chamber is terminated by a flat or slightly indented base that is expanded to form six rather broad, long, attenuate spines that contain extensions of the body chamber. In some specimens one or two Diagrammatic representation of Ancyrochitina cornigera n. sp., showing basal spines. Apical angle is indicated. X320. 20 ILLINOIS STATE GEOLOGICAL SURVEY spines may not be fully developed. In individuals where spines project horizontally (pi. 2, fig. 3) they give the appearance of a scalloped basal flange. One or two short, coarse spines may occur on the upper part of the neck or collar, otherwise the surface is smooth. The chamber wall is moderately thick. Remarks. - Ancyrochitina megastyla is closely related to Ancyrochitina cornigera, with which it occurs. They may be readily differentiated, however, in that megastyla possesses broad attenuate spines and cornigera has spike-like spines of circular cross section (text fig. 9). They also differ in neck length/over-all length ratios? cornigera ranges between 0.36 and 0.50 whereas megastyla gives ratios greater than 0.55. Like cornigera, megastyla is similar to both Ancyrochitina ancyrea and Ancyrochitina diabolo, but megastyla has a smaller apical angle than diabolo and does not have bifurcate spines like ancyrea. Measurements. - The following dimensions given in millimeters were measured with a micrometer ocular. Holotype: over-all length .181, body length .072, neck length .109, collar length, .022, max. spine length .036, body dia. .109, neck dia. .032, apical angle 45°. Paratype: over-all length .208, body length .059, neck length .118, collar length .022, max. spine length .014, body dia. .162, neck dia. .045, apical angle 49°. Derivation of name. - From Latin megastylus, meaning "having large spines." Occurrence. - Uncommon in bed three and rare in bed five, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P1-24 (holotype), 8P10-51, 8P17-24, 8P22-49 (paratypes). Fig. 9 - Diagram of Ancyrochitina megastyla n. sp. showing neck spines and the characteristic broad attenuate basal spines, x 300. Genus SPHAEROCHITINA Eisenack 1955 Type species: Sphaerochitina sphaerocephala (Eisenack) This genus was proposed by Eisenack for forms with subcylindrical necks; cone-, sphere-, or broadly mushroom-shaped body chambers; and essentially smooth CEDAR VALLEY CHITINOZOAN FAUNULE 21 walls that bear tiny tubercles or small, thick, erect spinules. The type species origi- nally was described from the Silurian Beyrichienkalk of the Baltic region. SPHAEROCHITINA PILOSA Collinson and Scott, n. sp. Plate 3, figures 1-5 This species occurs in greater numbers than any other in the Cedar Valley faunule. Its general shape is that of a long-necked erlenmeyer flask (text fig. 10). The conical body chamber has its greatest diameter very near the aboral end.. The apical angle averages 53°. The neck is distinct, cylindrical, slightly shorter than the body chamber, and terminated orally by a short, slightly flared translucent collar. Aborally the test is terminated by a flat to slightly convex base. The wall of the test is only moderately thick and ornamented with numerous, close-set, very fine spines. Some specimens denuded of spines appear to be smooth, although a careful inspection reveals the spine bases. Remarks. - Several species have the same shape as Sphaerochitina pilosa. Of these, Ancyrochitina ancyrea (Eisenack), Ancyrochitina diabolo (Eisenack), Ancyrochitina laguncula (Collinson and Schwalb) and Ancyrochitina spinosa (Eisenack) can be readily differentiated by gross differences in spine ornamentation. However, two species have been described that have no external ornamentation and therefore might be confused with denuded representatives of Sphaerochitina pilosa. The first of these, Sphaerochitina fungiformis (Eisenack), has a neck twice as long as the body chamber and can be distinguished from pilosa by that means. The second, Sphaerochitina sphaerocephala Eisenack, may be distinguished by its well rounded base. Measurements. - Dimensions for Sphaerochitina pilosa are given in table 1. Derivation of name. - From Latin pilosus, meaning "hairy." Occurrence. - Very abundant in bed three, common in bed five, occurs in beds four and six, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P1-25 (holotype), 8P25-24, 8P22-51, 8P17-3, 8P25-3 (all paratypes). Fig. 10 - Diagrammatic representation of Sphaerochitina pilosa n. sp. showing typical shape of test and distribution of short spines, X300. 22 ILLINOIS STATE GEOLOGICAL SURVEY (/) c 11 E u •V a. V) V ex >> H 71 Ui o 11 !/> h c r~- ri a cr rO r^ 1-1 o c O o O © in a to o ** fS fN X •* O © O "a *£"8Id8 m 00 o r- o o o c O - C o O o C © in 00 rr\ PM ir. o r- o ^3-£Zd8 00 SO m O c (N ™ a -"' — -i O c O ^ © in to o a. !-H c o cc rri o t~- £-<,3d8 00 c G> 1— 1 O c rsi in a I-H c © © © c © in c -e SO m I— * O fN c fs) O o k. IS-23d8 00 o o c C O o c rCi © O SO 43 a -e a. so o o r~- «-l o (N CO Wld8 f~ 00 e> » -* s >. u ■0 u M T3 o .- / ° > OJ id v a O P3 Z , ^ ■s ffl z < CEDAR VALLEY CHITINOZOAN FAUNULE 23 SPHAEROCHITINA SCHWALBI Collinson and Scott, n. sp. Plate 3, figures 6-10 Although not as abundant as Sphaerochitina pilosa, which it resembles, this species is common in most Cedar Valley samples. Its test, shaped like a short- necked erlenmeyer flask, has a conical body chamber with maximum diameter near the broad, slightly convex base. The sides of the chamber slope orad to form an apical angle of 75° to 80° and are quite distinct from the short cylindrical neck which is terminated orally by a short, transparent collar. The average ratio of neck length to over-all length is 0.35. With the exception of the collar, the entire surface of the test is densely covered by numerous very short simple spines (text fig. 11). Where these spines are broken, the spine bases impart a roughened texture to the surface. Remarks. - This species is closely related to Sphaerochitina pilosa, with which it occurs, but may be distinguished from it by the much shorter neck. The specimen illustrated on plate 3, figure 3, suggests transition between the two species. However, most specimens can be referred clearly to one or the other. The relatively broad base dis- tinguishes schwalbi from other short- necked, erlenmeyer-flask-like forms bearing simple spines (for example, Conochitina cactacea Eisenack). The ratio of the total width to total length of schivalbi is 5:7, but in cactacea it is only about 1:2. Measurements. - Dimensions for Sphaerochitina schwalbi are given in table 1. Derivation of name. - In honor of Howard Schwalb for his contribution to the study of Illinois chitinozoans. Occurrence. - Common in beds three through six, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P13-31 (holotype), 8P22-6, 8P2-24, 8P15-6, 8P18-52 (all paratypes). SPHAEROCHITINA NODULOSA Collinson and Scott, n. sp.. Plate 3, figures 15-19, 23, 25 The identifying characteristic of this very common species is its ornamentation, which consists of a few irregularly scattered, short, thornlike spines or rounded nodes confined to the aboral end of the body chamber. With this exception the test is Fig. 11 - Diagrammatic representation of Sphaerochitina schwalbi n. sp. showing characteristic short neck and short spines, X 350. 24 ILLINOIS STATE GEOLOGICAL SURVEY generally smooth. A few specimens bearing spines on the neck (for example, plate 3, fig. 18) have been observed. The test is shaped like an erlenmeyer flask with a gently convex aboral end and a conical body chamber that tapers gradually into the subcylindrical neck (fig. 12). Fig. 12 - Diagrammatic representations of (A) Sphaerochitina nodulosa n. sp. showing distribution of spines and nodes; (B) Sphaerochitina cf. S. nodulosa illus- trating thornlike spines and small apical angle. Both X320. Remarks. - In general form, Sphaerochitina nodulosa is similar to several other species, but in every case it may be distinguished by the nature and distribution of its spines: Sphaerochitina pilosa and Ancyrochitina cactacea (Eisenack) have spines on the oral half of the test; Ancyrochitina fragilis Eisenack, Ancyrochitina diabolo (Eisenack) and Ancyrochitina ancyrea (Eisenack) all have filamentous or branching spines near the maximum diameter; spines are lacking entirely in Sphaerochitina sphaerocephala (Eisenack) and Sphaerochitina fungiformis (Eisenack). The generic assignment of this species is not certain. Eisenack (1955) pro- posed the genus Sphaerochitina to include forms that are smooth, have only tiny tubercles, or very thick, erect, very small spinules. We believe that nodulosa fits into this category because of its nodular ornamentation. Only a few specimens hav- ing large spines have been observed. Measurements. - Dimensions for Sphaerochitina nodulosa are given in table 1. Derivation of name. - From the Latin nodulosus meaning "full of little nodes." Occurence. - Common in bed three, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P18-3 (holotype), 8Pl^i-21b, 8Pl6-21a, 8P1-23 (paratypes). CEDAR VALLEY CHITINOZOAN FAUNULE 25 SPHAEROCHITINA cf. S. NODULOSA Collinson and Scott Plate 3, figures 12, 14 Two well preserved specimens in our collections closely resemble Sphaerochitina nodulosa but differ from nodulosa in that the apical angle is much smaller (41° and 44 ), the body chamber is correspondingly longer (ratio of neck length/over-all length = 0.63, pi. 3, fig- 14), and it possesses thornlike spines rather than nodes. We are not certain whether these differences represent specific variation, or are significant enough to warrant erection of a new species. In either case, study of additional material will be necessary before a decision can be made. Occurrence. - Bed three, Solon member, Cedar Valley formation, near Milan, Illinois. Repository. - Illinois State Geological Survey, 8P1-44, 8P1-23. Genus EARLACHITINA Collinson and Scott, n. gen. Type species: Earlachitina latipes Collinson and Scott, n. sp. Our collections from the Cedar Valley formation contain a group of specimens sufficiently different from any previously described to warrant erection of a new genus. Earlachitina is proposed to include forms that are characterized by depressed subconical to subdiscoidal body chambers and subcylindrical necks terminated orally by a simple aperture. Specimens may or may not be collared. The base of the body chamber may be either slightly convex or concave and its periphery is ornamentated by a variable number of spines formed by prolongations of the body wall. A few spines may also be present on the neck and collar, otherwise, the surface of the test is smooth. The name is given in honor of Earl A. Collinson of the Collinson Stone Compa- ny which operates Milan quarry. Mr. Collinson, foster father of the senior author, accompanied him on collecting trips to the quarry and showed great interest in the project. EARLACHITINA LATIPES Collinson and Scott, n. gen., n. sp. Plate 2, figures 8, 9, 12-14, 20-24; plate 3, figures 13, 24 The distinctive subdiscoidal body chamber of Earlachitina latipes (text fig. 13) expands rapidly aborally forming a kind of flange referred to as the "aboral brim." Two to six (most commonly five or six) broad spines of variable length and develop- ment ornament the periphery of the brim. These are formed by the local projection of the body wall and contain extensions of the body chamber. The base of the body chamber is slightly concave. Orally the chamber tapers very rapidly from the brim. The apical angle is exceptionally large and ranges from 80 to 110 . The average chamber diameter is 0.112 mm.; the average over-all length only 0.054 mm. The juncture of chamber and neck is variable. In some specimens (pi. 2, fig. 8) the chamber tapers gradually into the neck, but in others (pi. 2, fig. 20) the juncture may 26 ILLINOIS STATE GEOLOGICAL SURVEY be quite distinct. The neck is relatively long and subcylindrical to cylindrical and and is terminated orally by a short, thin, translucent collar. The moderately thick chamber wall is smooth with the ex- ception of one or two short, stout spines that may be present on the collar or neck. Remarks. - This species is not closely similar to any previously de- scribed forms. It is similar to the speci- mens figured on plate 2, figures 6 and 10 as Earlachitina n. spp., but the latter differ in being smaller without definite brims and in possessing relatively small indistinct spines. Measurements. - The following dimensions are in millimeters and were determined with a micrometer ocular. Fig. 13 Diagrammatic representation of Earlachitina latipes n. gen., n. sp. showing neck spines, collar, brim and basal spines, X365- ^\^^ Specimen no. • • • • m • OS * CM »-^ CM •— < XT r<^ ro Ht r-j JL,