CnteA oucio ^ STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS, Director Three Ostracode Faunas from Lower and Middle Mississippian Strata in Southern Illinois Richard H. Benson Charles Collinson DIVISION OF THE ILLINOIS STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA CIRCULAR 255 ILLINOIS GEOLOGICAL SURVEY LIBRARY OCT 17 1958 1958 ilf-.^O'S STATE GEOLOGICAL SURVEY 3 3051 00003 8715 THREE OSTRACODE FAUNAS FROM LOWER AND MIDDLE MISSISSIPPIAN STRATA IN SOUTHERN ILLINOIS Richard H. Benson and Charles Collinson ABSTRACT Two outcrops in Union County have yielded ostracode faunas from three formations: The Springville Shale of the Valmeyer Series, and the Chouteau Limestone and Hannibal Shale of the Kinderhook Series. The fauna of the Springville is confined to the State Pond Mem- ber and is abundant and well preserved. It contains 21 species that represent 12 genera, of which the genera Graphladactyllis ,Kirkbya , Amphissites, and Roundyella are most abundant. Two species, Graphiadactyllls fernQlenensis Benson and Mauryella mammillata Ulrich and Bassler, seem to have stratigraphic significance. Four new species, Tetrasacculus ? stewartae, Monoceratina ? elongata, Amphissites springvillensis, and Graphiadactyllls ? unionensis are described. The fauna indicates that at least the lower part of the Springville (State Pond Member) is of the same age as the Fern Glen (early Valmeyer) . The fauna of the Chouteau also is abundant and contains 18 species that belong in 12 genera. Qualitatively, the fauna of the Chouteau is much like that of the Springville, but quantitatively it is distinctive in that Waylandella, Tetrasacculus ?, and Kirkbyel la are important numerically. Kirkbyella ozarkensis appears to have special significance for correlation of the Chouteau. Two new spe- cies from the formation, Waylandella dartyensis and Kirkbyel la an- nensis, are described. The fauna of the Hannibal is meager and only six species re- ferable to six genera were found. These species also are found in both the Springville and Chouteau Formations. INTRODUCTION Ostracode faunas of the lower and middle Mississippian rocks of North America have been virtually neglected by research workers. To date, less than half a dozen reports on the subject have been published, and much remains to be done before the fossils can be used effectively for stratigraphic or ecologic purposes. The two most recent papers dealing with Mississippian ostracodes (Benson, 1955; Echols and Gouty, 1956) described a fauna from the Fern Glen Formation (lower Valmeyer) of Missouri, and the present work was undertaken as an ex- tension of those reports. The fauna of the Springville Shale of southern Illinois was chosen for study because its stratigraphic position above the Chouteau [1] ILLINOIS STATE GEOLOGICAL SURVEY 20 ■ Alto Pass UNION %< nna Jonesboro COUNTY ■ Springville Limestone led us to suspect its early Valmeyer (Fern Glen) age. Prior to our study, which began in 1955, the Spring- ville Shale had been considered to be Kinderhook in age (Weller et al., 1948; Weller and Sutton, 1940). Investigation of two principal out- crops, one at State Pond (figs. 1, 3) and the other along Darty Creek (figs. 1, 2), yielded both ostracodes and co- nodonts not only from the Springville Shale but from the underlying Chouteau Limestone and Hannibal Shale. As the relationships and ages of the three lith- ologic units were undetermined, Collin- son and Scott (1958) undertook a separ- ate study designed to clarify the stra- tigraphy and to describe the conodont faunas. The stratigraphy used in this report follows their conclusions. STRATIGRAPHY The Springville, Chouteau, and Hannibal Formations of southern Illinois, which yielded the ostracodes for this study, crop out in a narrow, north-north- west trending belt that lies mostly with- in Union County but includes the north- east tip of Alexander County. The area is located on the east flank of the Ozark dome, and the formations are exposed in the west-central part of the county where they lap up onto the structure. In the western third of the county they have been removed by erosion. To the east of the outcrop belt they dip beneath the Hartline Chert Member of the Burlington-Keokuk Formation and younger rocks, but they continue in the sub- surface as far as southern Indiana where they crop out again. The Springville appears to be approximately equivalent to the New Providence, the Chouteau is the Rockford of Indiana, and the Hannibal is equivalent to at least part of the upper New Albany. The State Pond Member of the Springville Shale is the uppermost and most productive of the ostracode -yielding formations. The Springville is referable to the lower part of the Valmeyer Series. It is a bluish to greenish gray shale that weathers to variegated colors - white, red, and brown. The lower few feet, for which Collinson and Scott proposed the name State Pond Member, are soft and argillaceous but the upper part is silicified and hard. The average thickness of the formation is about 60 feet. In most outcrops it unconformably overlies the Grassy Creek Shale and is unconformably overlain by the Hartline Chert of Val- meyer age. Fig. 1. - Maps of Illinois and Union County showing location of collecting localities. No. 1. - Darty Creek lo- cality in NW{ SW{ sec. 11, T. 12 S., R. 2 W. No. 2. - State Pond locality, center S^ sec. 14, T. 12 S., R. 2 W. Both are in the Jonesboro quadrangle. o LOC. 1 - DARTY CREEK Q. E !° o £o Shale, greenish gray, poorly S2!^»„ UJ laminated, hard with green (— ^. _l vermicular markings. I5'± (~Cr~~^ 5 > Shale, greenish gray, \ i~~^T~~-~~ F E E z. laminated, hard, vermicular. \ r — — __^~— or \ i"^-^-— ' T a. in Shole, greenish gray, fissile, \ \ C -^~~~ black shale pebbles. \ \ (~-C^-~-"~~ Z> o \ \ Vi. ~~ — -~ Limestone, light brownish \ \ J"^:^--^^" T7 I qray. fine, very fossiliferous, \ ^tr-^^-— C~--^" " 1 6 o green chlorite streaks, r*S?~2i~~?5^ 1 l" to 2" calcite geodes. /ZiiSir^ESsJ I / / jg55^L^— ^jj S i J I Claystone, brownish gray, /lttl|l§tlt§§^ ■ ^ cole, limy nodules, silty. / e§H~f8|l§§^ or o Shale, black, carbon .fissile et§§§H§I§l§^ a OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS The Chouteau Limestone, where present, directly underlies the State Pond Member (figs. 2, 3) and is the uppermost unit in the Kinderhook Series. It is thin and discontinuous, not more than two or three feet thick. It is a dense, light gray, fine-grained argilla- ceous limestone and locally con- tains numerous brachiopods. The macrofauna (Savage, 19 20, p. 178) consists of Producte I la concentrica (Hall), Brachythyris semiplicata Hall, B. cf. B. pec u I iari s(Shumard), Ambocoelia unionensis Weller, and Cardlopsis cf. C radiata Meek & Worthen, and is compatible with the fauna of both the Rockford of Indiana and the Chouteau of west- ern Illinois. At the State Pond lo- cality (fig. 3), the Chouteau con- sists of discontinuous limestone lenses in a brown clay that yielded the ostracodes. At the Darty Creek locality (fig. 2), from which came the greater proportion of the total Chouteau ostracodes, the ostra- codes were found principally in a thin shale bed about 9 inches above the base. The Hannibal Shale, like the Chouteau, has been recognized only in the State Pond and Darty Creek outcrops. The limited distribution may be the result of an unconformity beneath the Springville, that is, between the Valmeyer and Kinderhook Series. In places the unconformity cuts through the Grassy Creek Shale so that the Springville Shale lies directly on Alto-Lingle Limestone of Devonian age. In southern Illinois the Hannibal is a greenish to brownish gray, slightly silty, soft shale or claystone. At Darty Creek it is a nonlaminated calcareous claystone and contains limy nodules. At State Pond, all but the upper three inches are laminated and some layers exhibit compaction laminae. Stratigraphic distribution of ostracodes and conodonts in the Hannibal are shown in figure 4. Fig. 2. - Collecting locality no. 1, Darty Creek, NW£ SW| sec. 11, T. 12 S., R. 2 W. , Jonesboro quadrangle, Union County, Illinois. Black sample intervals indicate zones that yielded ostracodes and/or co- nodonts. Bed 5 represents the State Pond Member of the Springville Shale . OSTRACODE FAUNAS Springville Shale The fauna of the Springville is both abundant and well preserved, but nearly the entire collection studied came from the lowermost 6 inches of the State Pond Member. More than 400 specimens were examined and many more were left unpicked in the samples. The varied fauna represents 21 species and 12 genera. It is dominated by the genera Graphladactyllis, Kirkbya, Bnirdin, Amphissites, and Roundyella so its Middle Paleozoic aspect is readily apparent, ILLINOIS STATE GEOLOGICAL SURVEY LOC. 2 - STATE DAM POND Shale, tannish to greenish gray, poorly laminoted, vermiculor, calcareous, few 1/8 mm guartz grains 10' Shale, dark green to black, with phosphate nodules. M/2 Shale, greenish gray, poorly laminoted 5" LU Shale, greenish gray, very calcareous, nodular. 2" Shale, greenish gray, poorly laminated, black pebbles. 6" Limestone, light gray, fine, glauconite phosphate pellets, lenses laterally to brown clay. 10" Shale, tannish gray, non- laminated. 3" Shale, greenish gray, hard, blocky. 6" Shale, greenish gray, sgueeze laminae 7 Three species numerically dominate the State Pond fauna (table 1). By far the most abundant is Grnphiadactyllis fern£lenensis Benson of which more than 150 specimens were examined. It is very abundant in the State Pond Shale but absent from the underlying Chouteau. The species is also found in the Fern Glen of Missouri, and it may prove to be a stratigraphic index for lower Valmeyer strata. Many more occurrences should be studied, however, before it is used without reservation as an index fossil. The second most abundant species is Graphiadacty I lis granopunctatus (Ul- rich & Bassler), which also occurs in the Fern Glen, Chouteau, and Bushberg ? of Missouri and the Ridgetop of Tennes- see. It is very abundant in the Chouteau in Union County but because of its stra- tigraphic range it appears to be of little value for detailed correlation. Kirkbya fernglenensis Benson is abundant in the State Pond Shale and is common in the Chouteau and in the Fern Glen of Missouri. We consider it to have value as a low-Valmeyer — high-Kin- derhook indicator. The species that has greatest prom- ise for use as a stratigraphic marker is Mauryella mnmmillata Ulrich & Bassler. It is known from the Fern Glen of Mis- souri and the Ridgetop of Tennessee as well as from the State Pond, but it is not known to occur either above or below lowermost Valmeyer beds. It has the further advantage of a distinctive ap- pearance that makes it recognizable even when poorly preserved. The fact that it is less than common in collections is, however, a disadvantage. Graphiadactyllis aff. G. lineatus (Ulrich & Bass- ler) occurs in the same formations as Mauryella mammillata Ulrich & Bassler but unfortunately is identifiable only when well preserved. Six new species, Waylandella dartyensis, Kirkbyella annensis, Tetrasac- culus ? stewartae, Monoceratina ? eloniata, Amphissites springvillensis , and Graphiadactyllis ? unionensis , are known from the State Pond Member, but all are shared with the Chouteau and four are also found in the Hannibal. Holo- types of the last four are from the Springville. In general aspect, the fauna of the Springville is essentially the same as that of the Fern Glen of Missouri, and there is little doubt in our minds that the State Pond Member of the Springville and the Fern Glen are correlative. Less Shale, black, fissile. 25 Fig. 3. - Collecting locality no. 2, State Pond, S\ sec. 14, T. 12 S., R. 2 W. , Jonesboro quadrangle. Union County, Illinois. Black sample inter- vals indicate zones that yielded os- tracodes and/or conodonts. Beds 2-7 are referable to the State Pond Mem- ber of the Springville Shale. OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS FORMATION SPRINGVILLE I HANNIBAL si SAMPLE NOS. 1 2 3 4 5 6 7 8 9 10 II 12 ostracodes U R R U u c conodonts U C C VA VA VA VA VA VA u u u SAMPLE NOS. 7 6 5 4 3 2 1 ostracodes VA A U R conodonts VA A A C Fig. 4. - Relative abundance of ostracodes and conodonts according to sample, formation, and outcrop. R = rare; U= uncommon; C = common; A = abundant; VA = very abundant. certain is the correlation with the Ridgetop of Tennessee, although the presence of Mauryella mammillnta in both seems significant. The only species which qualitatively differentiate the fauna of the State Pond from that of the underlying Chouteau are Graphiadactyllis fernglenens is Benson, G. aff. G. lineatus (Ul- rich & Bassler), and M. mammillata Ulrich & Bassler, but because G. fernilen- ensis is so abundant in the State Pond Shale, the general appearance of the two faunas is quite different. Chouteau Limestone Numerically, the Chouteau ostracodes are only slightly less abundant than those of the State Pond Member. The Chouteau fauna is also almost as varied, having 18 species referable to 12 genera (table 1). Six species are new. The holotypes of Way lande I la dartyensis and Kirkbyella annensis are from the Chouteau. All species of the southern Illinois Chouteau are found in the State Pond Shale, but differences in abundance of shared species give the two faunas dis- tinctive appearance. For example, Way lande I la dartyensis, n.sp., Tetrnsac- culus ? stewartae , n.sp., Kirkbyella ozarkensis Morey.and Graphiadactyllis moridiei Benson are more than twice as abundant in the Chouteau as in the State Pond Member, and the very distinctive species, Kirkbyella annensis, n. sp., is abundant in the Chouteau but rare in the State Pond. The most abundant species is Graphiadactyllis iranopunctatus (Ulrich & Bassler), of which more than a hundred specimens came from the Chouteau. Bairdia&ii. B. kinder hookens is Morey and B. aff. B. mainacurta Morey are next in abundance, and they are followed by Amphissites sprinQvillensis. Seven of the eighteen species (table 1) found in the southern Illinois Chou- teau also are present in the Chouteau of Missouri (Morey, 19 36), which contains twelve species. In addition to the seven species common to both faunas, three other species, Kirkbyella ? dubia Morey, Amphissites centronotus (Ulrich & Bassler), and Healdia decora Morey, appear closely related to species in our fauna. The two faunas are therefore quite similar, even though it is likely that Morey's fauna came from Chouteau beds older than any present in Union County. ILLINOIS STATE GEOLOGICAL SURVEY Table 1. - Stratigraphic Occurrences of Lower and Middle Mississippian Ostracode Species in Southern Illinois and Adjacent States C 3 1 s o « a; m (JL, O o 3 -^ (0 fcj ■M O 3 to O co o £ o o a -r-t u a ■a c o a. o ■4-* (0 3 0) E 0) 5 3 fO 0) •M 3 o XI O ■ — 1 (0 Xi c a ra X X X - Paraparchites nicklesi (Ulrich) R R R X X - - Bairdia aff. B. kinderhookensis Morey C A - X X X - B. aff. B. magnacurta Morey C A - X - - - Healdia sp. R R R? ? - - - Waylandella dartyensis, n.sp. R U R ? - - - Tetrasacculus ? stewartae, n.sp. U C U - - - - Monoceratina ? elongata, n.sp. u U U - - - - M. cf. M. ardmorensis (Harlton) u u - X - - - Kirkbya fernglenensis Benson A c - - - - - Kirkbyella annensis, n.sp. R A - - X - - K. ozarkensis Morey R c - - - - - Amphissites springvillensis, n.sp. C A R X - - - Graphiadactyllis ? unionensis, n.sp. U R - X X X X G. fayettevillensis (Harlton) u R - X - - - G. fernglenensis Benson VA - - X - - - G. moridgei Benson R C - X X X X G. granopunctatus (Ulrich & Bassler) A VA - X - - X G. aff. G. lineatus (Ulrich & Bassler) U - - X - - X Mauryella mammillata Ulrich & Bassler U - - X X *~ ™" Roundyella mopacifa Benson R. ? sp. C U U u ~ R = rare (<5 per 1000 gms). U= uncommon (5-10 per 1000 gms) C = common (10-20 per 1000 gms). A = abundant (20-50 per 1000 gms). VA = very abundant (50+ per 1000 gms), X = present. Hannibal Shale The ostracode fauna of the Hannibal Shale, the first to be described from the formation, is meager and has no significant stratigraphic implications. The fauna consists of six species referable to six genera (table 1). All are found in both the Chouteau and Springville Formations. The ostra codes, in our opinion, probably come from the uppermost part of the Hannibal as the formation is developed in its type area of northeastern Mis- souri and western Illinois. The Hannibal in Union County therefore may be equivalent to some of the Chouteau beds in the Chouteau type area in western- central Missouri. OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS Table 2. - Stratigraphic Ranges of Genera Represented in the Collections from State Pond and Darty Creek Localities Period c C ia ro -iH 1-1 c a. c rO c o. ■i-i > o c to w i 1 d o -i-i > (0 a to (0 w Genus o ■a O In • — 1 -i-H o > Q en s C C a) 1 i-. a) a, ro •rH H Kirk by a Bairdia Tetrasacculus Kirkbyella Graphiadactyllis Amphissites Paraparchites Monoceratina Mauryella Waylandella Roundyella Healdia SYSTEMATIC PALEONTOLOGY Family LEPERDITELLIDAE ? Ulrich & Bassler, 1906 Genus PARAPARCHITES Ulrich & Bassler, 190 6 Type species: Paraparchites humerosus Ulrich & Bassler PARAPARCHITES NICKLESI (Ulrich), 1891 Plate 1, figure 9 Leperditia nicklesi ULRICH, 1891, Cincinnati Soc. Nat. Hist. Jour., v. 13, p. 200, pi. 18, figs. la-c. Paraparchites n ick les i GRABAU & SHIMER, 1910, North American Index Fossils, p. 343, figs. 1657 c-f. Paraparchites cf. P. nicklesi (Ulrich) BENSON, 1955, Jour. Paleontology, v. 29, p. 1038, pi. 108, figs. 8, 14. Diagnosis . - This species can be recognized by the presence of a small, sometimes very indistinct, node or spine (formerly referred to as an eye spot) located on the postero-dorsal side of the right valve. Remarks . - The postero-dorsal spine or node is very subdued in the spec- imens found in the Springville but can be found on all right valves of mature instars. Stratigraphic occurrence . - Chouteau, Fern Glen, Springville (State Pond Member), and Warsaw Formations and strata up to and including lower Penn- sylvanian. Material studied . - Only six specimens were found. Reposited under cat- alog numbers 9P1 (figured specimen) and 9P2 (other specimens). 8 ILLINOIS STATE GEOLOGICAL SURVEY Family BAIRDIIDAE Sars, 1887 Genus BAIRDIA McCoy, 1844 Type species: Bairdia curta McCoy BAIRDIA aff . B. KINDERHOOKENSIS Morey, 19 36 Plate 1, figures 7, 8 Bairdia kinder hookens is MOREY, 1936, Jour. Paleontology, v. 10, p. 120, pi. 17, figs. 13, 15. anterior flange Diagnosis . - This species can be recognized by its long, gently concave, postero-dorsal slope and acuminate pos- terior end. The central portion of the carapace is strongly tumid. Remarks. - The specimens in our collections are almost identical to those originally described from the Chouteau by Morey (19 36) except that the break in slope of the anterior end is not as pronounced. This slight difference is not thought to be sufficient to warrant description of a new species. Morey's specimens are also somewhat larger (1.91 mm. by 1.10 mm. by 0.70 mm.) than those figured here (1. 10 mm. by 0.70 mm. by 0.55 mm.). Only one specimen was found that came near the size he described. It is probable that our small specimens represent young in- stars and that only one mature specimen was found. Stratigraphic occurrence . - Chouteau Limestone of Missouri and Illinois; Springville Shale of Illinois. Material studied . - Thirty-five specimens were examined. Reposited under catalog numbers 9P3, 9P4 (figured specimens) and 9P5 (other specimens). muscle scar Fig. 5. - Bairdia aff . B. kinderhooh- ensis Morey. Top, lateral view il- lustrating valve overlap and punc- tate surface texture. Bottom, in- terior of left valve showing shape of flange and hingement and loca- tion of muscle scar. X30 and X40 respectively. BAIRDIA aff. B. MAG NACURTA Morey, 19 35 Plate 1, figures 10, 11 lirdia mainacurta MOREY, 1935, Jour. Paleontology, v. 9, p. fig. 22; ibid., 1936, v. 10, p. 118, pi. 17, figs. 16, U 323, pi. 28, Diagnosis . - This species can be recognized by its rather short and acute posterior end, evenly arched dorsal margin, short anterior end, and over- all rounded shape. Remarks. - The specimens found in the Springville (State Pond Member) and Chouteau Formations are very close to B. mainacurta from the Bushberg? as illustrated by Morey (19 35). Our specimens differ, however, by possessing a slightly higher posterior end that gives the venter a more rounded outline in OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS anterior side view. Our forms are much closer to representatives from the Chouteau Formation figured by Morey (19 36, pi. 17, fig. 18). In addition to the above characteristics the Springville specimens have a punctate sur- face and exhibit a wide, welded duplica- ture as well as a partial bairdioid muscle scar pattern. The hinge is short and partial- ly obscured because of poor preservation. Our species is similar to B. beedei Ulrich and Bassler as illustrated by Cooper (1946, p. 41, pi. 1, figs. 35-40) except that the ventral and dorsal overlap is not as great in our species. Our specimens are closer to B. augusta Cooper (1946, p. 41, pi. 1, figs. 41-44) whose surface is smooth. Stratigraphic occurrence . - Bushberg ? of Missouri, Chouteau Formation of Mis- souri and Illinois, and the Springville (State Pond Member) Formation of Illinois; all of lower Mississippian age. Material studied . - Thirty-five specimens were found. All are reposited under catalog numbers 9P6, 9P7 (figured specimens) and 9P8 (other specimens). muscle scars Fig. 6. - Interior view of right valve of Bairdia aff. B. magna- curta Morey showing the dupli- cative as well as location of muscle scars. X40. Family HEALDIIDAE, Harlton, 19 33 Genus WAYLANDELLA Coryell & Billings, 19 32 Type species: Waylandella spinosa Coryell & Billings Waylandella CORYELL & BILLINGS, 1932, Am. Midland Naturalist, v. 13, no. 4, p. 175; COOPER, 1946, Illinois Geol. Survey Bull. 70, p. 63. WAYLANDELLA DARTYENSIS Benson & Collinson, Plate 1, figures 4, 5, 6 n. sp. anterior posterior spine Fig. 7. - Interior view of right valve of Waylandella dart yen- sis, n.sp., showing the inner margin, lack of duplicature, and simple hinge. X40. Diagnosis . - This species can be recognized by the high, broadly arched dorsum of the left valve and the presence of a small spine on the postero-venter. Description . - Carapace small to medium sized, subovate to elliptical in lateral view; oblong to ovate in dorsal view with the outline broken only by the two projecting posterior spines. Dorsum of right valve broadly arched; higher and more sharply arched in left valve; venter is straight to slightly concave dorsally; ends of both valves rounded in adult in- stars but posterior may be blunt in im- mature stages. Surface smooth except for the pres- ence of a small spine on the postero-ven- ter near the margin of both valves. In- 10 ILLINOIS STATE GEOLOGICAL SURVEY terior features were obscure but the hinge structure appeared to be very simple and no duplicature was observed. Left valve appears to over-reach but does not overlap right valve. Holotype length, 1.05 mm.; height, 0.63 mm.; width, 0.50 mm . Remarks . - Representatives of this genus are uncommon in the lower and middle Mississippian. Waylandella dart yens is is very similar to W. obesa Cooper and V. symmetrica Cooper (1946, p. 65, pi. 7, figs. 17-76), which were described from the Pennsylvanian of Illinois. Thus, the genus has a long stratigraphic range. Our species is quite different from the type W. spinosa Coryell & Billings, which might be confused with some representatives of the genus Cave I Una. Obviously more work needs to be done on the genus Way Ian - della before it can be considered very useful. We have placed it in the family Healdiidae because of the apparent direction of over-reach and the presence of posterior spines and an arched dorsum. Derivation of name . - Darty Creek locality from whence the type specimens came. Stratigraphic occurrence . - Hannibal, Chouteau, and Springville (State Pond Member) Formations of southern Illinois. Material studied . - Fifteen specimens were considered. Specimens re- posited under catalog numbers 9P9, 9P10 (cotypes from sample 4, Darty Creek locality), 9P11 (figured paratype) and 9P12 (unfigured paratypes). Family PRIMITIIDAE Ulrich & Bassler, 19 2 3 Genus TETRASACCULUS Stewart, 19 36 Type species: Tetrasacculus bilobus Stewart Tetrasacculus STEWART, 1936, Jour. Paleontology, v. 10, p. 744. TETRASACCULUS ? STEWARTAE Benson & Collinson, n.sp. Plate 4, figures 1-5 Diagnosis . - This species can be recognized by the development of three pairs of large, spherical brood pits or scalloped swellings along the anterior and ventral margins of the female, plus a shallow sulcus; the male possesses a small a ntero -ventral spine on each valve. Description . - Carapace small to medium in size; subquadrate to subovoid in lateral view. Greatest length just ventral to dorsum; greatest height just an- terior to midpoint; hinge line straight, occupying all of dorsal margin; free mar- gin broadly arched, skewed toward the antero-venter. Subovate in dorsal view of male, obovate in female. Surface finely reticulate with a simple but pronounced linear sulcus gently curving toward the antero-venter from the dorsum and emphasized by the slight swelling in the posterior end that forms an elongate lobe. No nodes are present. Female has three pairs of large, spherical brood pits along the anterior and ventral margins; male is almost identical to the female but possesses small spines in lieu of the brood pits and is slightly smaller. Valves are equal. Internal structures and hinge were obscure. Length of holotype 0.80 mm.; height, 0.48 mm.; width, 0.50 mm. Remarks . - We are somewhat dubious about placing this species in the genus Tetrasacculus because, even though it is very similar to other species of this genus, it contains only three pairs of brood pits instead of four. It may be possible, however, that the specimens studied were not mature and if an OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 11 adult had been found it might have had four pairs of brood pits. The smaller or younger female instars found possessed only two pairs of brood pits. The presence of brood pits on the younger females casts doubt on the theory that these structures were used by the female to carry her young. It also may be evidence that reproduction is not always confined to the last instar stage. This species is similar to T. loculata (Ulrich), formerly placed in the genus Cteno - bolbina (Ulrich, 1900, p. 184), which pos- sesses four pairs of brood pits and is found in the Ridgetop Shale of Tennessee. Derivation of name . - In honor of Grace Anne Stewart. Stratigraphic occurrence . - Hannibal, Chouteau, and Springville (State Pond Mem- ber) Formations of southern Illinois and possibly the Fern Glen Formation of Missouri, Material studied . - Thirty specimens were considered. Specimens reposited under catalog numbers 9P13, 9P14 (cotypes from sample 5 at Darty Creek locality), 9P15-17 (figured paratypes), and 9P18 (un- figured paratypes). Family ACRONOTELLIDAE Swartz, 19 36 Genus MONOCERATINA Roth, 1928 Type species: Monoceratina ventrale Roth sulcus antero-ventral spine anterior brood pits Fig. 8. - Tetrasacculus stewartae, n.sp. Top, lateral view of right valve of male carapace showing sulcus and anterior spine. Bottom, right lateral view of female carapace show- ing brood pits. All X40. MONOCERATINA ? ELONGATA Benson & Collinson, n.sp. Plate 3, figure 14 Diagnosis . - This species can be recognized by its long hinge and the presence of a node anterior to the midventer. Alae are characteristic of the genus. Description . - Carapace small, fragile, long and narrow in lateral and dorsal views. Hinge straight with a broadly arched ventral margin skewed toward the anterior end, forming a long pointed posterior end and a shortly rounded anterior. Both cardinal angles obtuse; small, short alae project from the midventer. Hinge structure obscure. Surface finely granulose with a node located just anterior to midventer. Length of holotype, 0.65 mm.; height, 0.28 mm.; width, 0.25 mm. Remarks . - This species is doubtfully assigned to the genus Monoceratina; may be a form intermediate between Monoceratina and the genus Triceratina The former typically has no nodes, whereas the latter has two. Our species bears one node and is more elongated than typical Monoceratina, somewhat like the elongate forms of Triceratina . Derivation of name. - From its elongate shape. 12 ILLINOIS STATE GEOLOGICAL SURVEY EXPLANATION OF PLATE 1 All magnifications X40 Figure 1,2. - Graphiadactyllls fayettevi liens is (Harlton) . 1. - Exterior of right valve showing fingerprint sur- face pattern and postero-dorsal spine. 2. - Ex- terior of right valve of late ins tar. 3. - Graphind.actyllis3.if. G. lineatus (Ulrich & Bassler). Exterior of right valve showing variation in finger- print surface pattern and small postero -ventral spine. 4-6. - Waylandella dartyensis Benson & Collinson, n.sp. 4, 5. - Exterior of right valves showing outline, sur- face texture and posterior spine. 6. - Exterior of left valve showing shape of valve with posterior spine. 5 and 6 are cotypes. 7,8. - Bairdiaafi. B. kinder hookens is Morey. 7. -Left valve showing marginal area. 8. - Exterior of right valve showing overreach of left valve and long pos- tero-dorsal slope (specimen canted slightly with dorsum toward viewer) . 9. - Paraparchites nicklesi (Ulrich) . Exterior of right valve of mature instar showing postero-dorsal spine accentuated by coating (foreign matter in antero- dorsal region). 10,11. - Bairdia aff. B. magnacurta Morey. 10. - Interior of right valve showing marginal features. 11. - Ex- terior of a right valve showing shape, overreach, and surface texture. Illinois State Geological Survey Circular 255. Plate 1 Benson & Collinson — Threk Ostracode Faunas from Southern Illinois Illinois State Geological Survfy Circulai i .tf: 2 Benson & Collinson —Three Ostracode Faunas fr< hern Illinois OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 13 EXPLANATION OF PLATE 2 All magnifications X40 Figure 1-4. - Graphiadactyllis moridgei Benson. 1. - Exterior of left valve showing fingerprint-like pattern, elon- gate shape, and anterior and posterior spines. 2-4. - Exterior views of right valves showing sur- face pattern and shape. 5-8. - Graphiadactyllis unionensis Benson & Collinson, n. sp. 5. - Exterior of right valve of holotype show- ing faint fingerprint surface pattern and posterior and anterior spines. 6. - Interior view of left valve of paratype showing the narrow marginal area and the hinge. 7. - Exterior of right valve of paratype. 8. - Exterior of left valve of paratype. 9-11. - Graphiadactyllis granopunctatus (Ulrich & Bassler). 9. - Exterior view of late instar. 10. - Exterior of right valve of adult. 11. - Exterior of left valve of adult. All show granopunctate surface texture and the central smooth spot over the muscle scar. 14 ILLINOIS STATE GEOLOGICAL SURVEY Stratigraphic occurrence . - Hannibal, Chouteau, and Springville (State Pond Mem- ber) Formations of southern Illinois. Material studied . - Nineteen speci- mens were considered, all single valves. Reposited under catalog numbers 9P19 (holotype from sample 5 at Darty Creek locality) and 9P20 (paratypes). MONOCERATINA cf. M. ARDMORENSIS (Harlton), 1927 Plate 3, figure 13 Cythereis ? ardmorensis HARLTON, 1927, Jour. Paleontology, v. 1, p. 211, pi. 33, figs. 14 a-c; Am. Jour. Sci., ser. 5, v. 5, p. 270, pi. 2, figs. If Monoceratina ardmorensis HARLTON, 19 33, pi. 7, figs. 14 a, b. anterior sulcus nodes Fig. 9. - Monoceratina ? eloniata, n. sp. Lateral view of right valve showing sulcus, nodes, and sur- face texture. X40. a, b. Jour. Paleontology, v. 7, P. 21, Description . - Carapace small, elongate, subrectangular in lateral view; elliptical, modified by development of curved alae, in dorsal view. Hingeline straight, running almost full length of the carapace, ventral margin broadly arched, both ends blunt, alae swing posteriorly from the anterior end terminating in close to the postero-venter of the main part of the carapace. Maximum length along midline; greatest height and width just posterior to midpoint. Surface smooth. Length of figured specimen 0.58 mm.; height, 0.25 mm.; width, 0.50 mm. Remarks . - Many forms have been as- Harlton ■anterior postero-ventral spine curved Fig. 10. Monoceratina cf. M. ardmorensis (Harlton). Top, lateral view of left valve showing postero-ventral spine and illustrating the surface texture. Bottom, ventral view of right valve showing well developed curved ala. X40. signed to Monoceratina ardmorensis that probably should be distinct species in their own right. However, because the number of specimens related to this form are always few in any faunal collection, not enough is known about its true variability and stratigraphic range to subdivide it properly at this time. For this reason our specimens are conditionally consi- dered comparable to this species. They are more elongate and less triangular in dorsal view than M. ardmorensis and lack the spines but are similar in marginal outline. Stratigraphic occurrence . - This species is usually found in lower Pennsylvanian strata. Found also in Springville (State Pond Member) and Chouteau Formations of southern Illinois. Material studied . - Twelve specimens were found. Reposited under catalog numbers 9P21 (figured specimen) and 9P22 (all others). OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 15 Family KIRKBYIDAE Ulrich & Bassler, 1916 Genus KIRKBYA Jones, 1859 Type species: Klrkbya permiann (Jones) KIRKBYA FERNGLENENSIS Benson, 1955 Plate 4, figures 12-14 Kirkbya fernglenensis BENSON, 1955, Jour. Paleontology, v. 29, p. 1036, pi. 107, figs. 11, 13, 17, 1G. Diagnosis . - This species can be recognized by its large size, distinct shoulders, wide velum, and large kirkbyan pit. Stratigraphic occurrence . - Originally described from the Fern Glen For- mation and now found in the Springville and Chouteau Formations of southern Illinois. Material studied . - Sixty specimens found, all single valves, representing all instar stages. Reposited under catalog numbers 9P23-26 (figured specimens) and 9P27 (all other specimens). Genus KIRKBYELLA Coryell & Booth, 19 33 Type species: Kirkbyella typa Coryell & Booth Kirbbye I la CORYELL & BOOTH, 1933, Am. Midland Naturalist, v. 15, no. 3, p. 262. KIRKBYELLA ANNENSIS Benson & Collinson, n.sp. Plate 4, figures 9-11 Diagnosis . - This species can be distinguished from others of its genus by the lack of a pronounced lateral ridge and by the development of a short blunt spine on the postero-ventral part of each valve. Description . - Carapace medium-sized, subrectangular in lateral view. Greatest length through the mid-portion; dorsum and venter are approximately parallel and straight; both ends are about equally subrounded tangent to the venter, forming obtuse cardinal angles. Subovate in dorsal view, altered slight- ly by postero-ventral spines; subtriangular as viewed from anterior. Only individual valves were found, and valve relationship is therefore not known. The valve walls are moderately thick, but not robust. The surface is ornamented by a closely reticulate pattern punctuated by a short blunt postero-ventral spine and a shallow but well defined S2 sulcus. Unlike many species of the genus, this one has no prominent ridge developed parallel to the venter. Internal features were obscure in the specimens examined. Young instars exhibited all of the features characteristic of the species but the spine is not well developed until the later stages. Length of holotype 0.83 mm.; height, 0.45 mm.; width, 0.35 mm. Remarks . - This species is similar in appearance to A', unicornis Coryell & Malkin (1936, p. 5, fig. 13) except for the lack of the conspicuous ridge ex- tending toward the anterior from the posterior spine. K. annensis differs from the type species, K. typa, in its lack of ridge development and the presence of a postero-ventral spine. Derivation of name . - From the city of Anna in southern Illinois near the collecting locality. 16 ILLINOIS STATE GEOLOGICAL SURVEY EXPLANATION OF PLATE 3 All magnifications X40 Figure 1-4. - Roundyella mopacifa Benson. 1. - Exterior of left valve showing slightly expanded anterior end and nodes. 3. - Exterior of right valve. 2, 4. - Exte- rior views of respective right and left valves of in- stars. 5. - Graphiadactyllis moridi el Benson. Interior view of left valve showing the development of the margin, the hinge, and the faint trace of the muscle scar. 6-8. - Mauryella mammillata Ulrich & Bassler. 6. -Exte- rior view of left valve showing node development, surface texture, and shallow sulcus. 7. - Exterior left valve of early instar with only five nodes. 8. - Exterior left valve of late instar showing faint sixth node. 9, 10. -Roundyella ? Sp. Exterior views of left ? valves showing development of four nodes in early and late ins tars. 11, 12. - Graphiadactyllis fernglenensis Benson. 11. - Exte- rior of left valve of late instar. 12. - Exterior view of left valve of adult showing detailed surface pat- tern with differentiation around area of muscle scar. 13. - Monoceratinn cf. M. ardmorensis (Harlton) . Exte- rior view of left valve. 14. - Monoceratina ? eloniata Benson & Collinson, n.sp. Exterior view of right valve of holotype. Illinois State Geological Survey Benson & Collinson — Three Ostracode Faunas from Southern Illinois Illinois State Geological Survey '!i« n.AK 255. Plate i Benson & Collinson — Three Ostracode Faunas from Southern Illinois OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 17 EXPLANATION OF PLATE 4 All magnifications X40 Figure 1-5. - Tetrasacculus ? stewartae Benson & Collinson, n.sp. 1. - Exterior of right valve of male with posterior spine. 2. - Exterior of left valve of male (cotype) with posterior spine. 3, 4, 5. - Exterior views of left valves of females illustrating the development of the brood pouch; 4 represents a cotype. 6-8. - Kirkbyelln ozarkens is Morey. 6. - Exterior view of right valve of a late instar. 7. - Exterior view of a left valve of a late instar. 8. - Exterior of right valve of adult showing the lateral spine, ridge and sulcus. 9-11. - Kirkbyella annens is Benson & Collinson, n.sp. 9. - Exterior left valve of the holotype. 10. - Ex- terior of left valve of late instar. 11. - Exterior of right valve of late instar. All show the posterior spine and sulcus. 12-14. - Kirkbya fernilenens is Benson. 12. - Exterior of right valve of early instar. 13. - Exterior of right valve of late instar. 14. - Exterior of left valve of adult. 13 and 14 show development of kirkbyan pit. 15-16. - Amphissites springvillensis Benson & Collinson, n.sp. 15. - Exterior right valve of late instar show- ing incomplete development of the carina. 16. - Ex- terior of right valve showing the chipped holotype with complete development of the carina. 18 ILLINOIS STATE GEOLOGICAL SURVEY Stratigraphic occurrence . - Chouteau and Springville (State Pond Member) Formations of southern Illinois. Material studied . - About 35 specimens were considered. Specimens re- posited under catalog numbers 9P28 (holotype), 9P29, 9P30 (figured paratypes) and 9P31 (unfigured paratypes). KIRKBYELLA OZARKENSIS Morey, 19 36 Plate 4, figures 6-8 Kirkbyella orarkens is MOREY, 1936, Jour. Paleontology, v. 10, p. 118, pi. 17, fig. 1. Diagnosis . - This species is distinguished by its broad, shallow sulcus and its long prominent ridge that is located below the sulcus and runs parallel to the dorsum. The ridge terminates in a blunt spine near the posterior. Stratigraphic occurrence . - Originally described from the Chouteau For- mation of Green and Boone counties in Missouri. Also found in the Springville (State Pond Member) and Chouteau Formations of southern Illinois. Material studied . - Twenty-three specimens were found. Reposited under catalog numbers 9P32-34 (figured specimens) and 9P35 (all other specimens). Subfamily AMPHISSITINAE Knight, 19 28 Genus AMPHISSTTES Girty, 1910 Type species: Amphissltes rugosus Girty Amphlssites GIRTY, 1910, N. Y. Acad. Sci. Ann., v. 20, p. 235; KELLETT, 1935, Jour. Paleontology, v. 10, p. 772. AMPIIISSITES SPRINGVILLENSIS Benson & Collinson, n.sp. Plate 4, figures 15-16 Diagnosis . - This species can be distinguished from others of its genus because the subcentral node is almost completely enveloped by carinae that join at the dorsum and are separate below the subcentral node. Description . - Carapace large, in general robust but with delicate cari- nae and vela, subrectangular in lateral view. Greatest length just above mid- line; greatest height near mid-length; hingeline straight, ventral margin gently arched with both ends curving and terminating in a slightly obtuse angle with the hingeline. Elongate subrectangular in dorsal view; widest in the region of the sub- central node. Blunt, wedge-shaped in end view. Valve relationship not known because only single valves were found. Valve walls moderately thick. Interior structures are a simple reflection of the exterior with such details as hinge and muscle scar obscured; preservation of these structures poor. Surface ornamentation is an irregular reticulate pattern out of which the carinae are developed. The pattern covers the subcentral node and tends to be carried into the wide velum that originates at the cardinal angles and continues around the venter subparallel to the free margin. The subcentral node has a re- ticulate surface pattern and is fairly large in diameter and prominent in some specimens. In others it tends to be smaller in diameter but remains high. The carinae are best developed at the quarter lengths along the hingeline, continuing OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 19 node carina outer flange (in the more mature forms) to join along the dorsum, tending to circumscribe the subcen- tral node to form an enclosing rectangle, but remaining unclosed below the subcentral node. The anterior portion of this carina generally is more prominently developed than the posterior. The kirkbyan pit is very subdued and sometimes difficult to observe. Three to four rows of network openings separate the velum from the ventral margin in the mature instars; there are fewer rows in the immature stages. This feature is difficult to determine in most specimens. The development of the carinae also show quite a bit of variability. Length of holotype 1.30 mm.; height, 0.83 mm.; width, 0. 60 mm. Remarks . - This species bears a close resemblance, and may be related, to A. simi- lar is Morey (19 36) described from the Chou- teau Formation of Missouri. In the Missouri species, however, the velum is carried much higher on the side of the valve than in our species. A. rugosus Girty, described from the Fayetteville Shale of Arkansas, is quite different from ours. It has a relatively larger but more subtle subcentral node and carinae that surround the node and appear to be almost like secondary vela. Unfortunately, the young instars of A . sprinivillensis are difficult to identify, and only a few good fully mature specimens were found. Derivation of name . - From the village of Springville. Stratigraphic occurrence . - Hannibal, Chouteau, and Springville (State Pond Member) Formations of southern Illinois. Material studied . - Forty-nine specimens were considered. Specimens reposited under catalog numbers 9P35 (holotype from sample 5 at Darty Creek locality), 9P36 (figured paratype) and 9P37 (unfigured paratypes). Fig. 11. - Amphissites sprini- villensis ,n.sp. Lateral view showing large subcentral node, well developed inner carinae with ventral extensions and wide, plain, outer flange. X40. Family QUASILLITIDAE Coryell & Malkin, 19 36 Genus GRAPHIADACTYLLIS Roth, 19 29 Type species: Graphiadactyllis arkansana (Girty) Graphiodactyllis ROTH, 1929, Wagner Free Inst. Sci. Publ. no. 1, p. 10. Graphiadactyllis Roth, BENSON, 1955, Jour. Paleontology, v. 29, p. 1033. GRAPHIADACTYLLIS ? UNIONENSIS Benson & Collinson, Plate 2, figures 5-8 n. sp. Graphiadactyllis cf. G. cornutus (Ulrich & Bassler) BENSON, 1955, Jour. Paleontology, v. 29, p. 1035, pi. 107, figs. 1-3, 9. Diagnosis . - This new species can be recognized by the angularity of the outline of the carapace as seen in lateral view; the lack of convexity of the valves as seen from the dorsal view; the delicate fingerprint-like surface pattern, and the usual presence of two small spines on the postero-dorsum and venter. 20 ILLINOIS STATE GEOLOGICAL SURVEY Description . - Carapace small to medium sized, compressed in dorsal view, subquadrate in lateral view. Hingeline straight, venter straight converg- ing toward dorsum posteriorly, both ends straight and subparallel, corner rounded at a ntero -venter. Greatest length just below the midline; greatest height in anterior end; greatest thickness in posterior end. Surface ornamented with the fingerprint-like pattern commonly found in the genus Graphiadactyllis. Two small spines are located on the postero-dor- sum and venter of each valve. Several specimens exhibit a third spine on the antero-ventral margin. The hinge is not as boldly developed as is typical of the genus Graphia- dactyllis. No duplicature or pore canals could be seen but a rough circular muscle scar, typical of the family Quasillitidae, was observed. Length of holotype 1.00 mm.; height, 0.48 mm.; width, 0.25 mm. Remarks . - The poorly preserved specimens described from the Fern Glen Formation as Graphiadactyllis cf. G. cornutus (Ulrich & Bassler) are sufficiently similar to this species to be included in it. The similarity should be noted be- tween G. unionensis and certain variations in the species described by Swartz and Oriel (1948, pi. 79, fig. 21; pi. 80, fig. 6) as Quasillites binodosus and Q. lobatus from the Windom Beds (Devonian) of New York. This serves to point out the relationship between the genera Quasillites and Graphiadactyllis and illustrates the difficulty of separating some of the species of the two genera. Derivation of name . - From Union County, Illinois. Stratigraphic occurrence . - Chouteau and Springville (State Pond Member) Formations of southern Illinois and the Fern Glen Formation of Missouri. Material studied . - Eleven specimens were considered. Reposited under catalog numbers 9P38 (holotype from bed 5 at Darty Creek locality), 9P39-41 (figured paratypes) and 9P42 (unfigured paratypes). GRAPHIADACTYLLIS FAYETTEVILLENSIS (Harlton), 19 29 Plate 1, figures 1, 2 Bassleria fayettevillensisB.ARL'ION, 1929, Am. Jour. Sci., ser. 5, v. 18, p. 256, pi. 1, figs. 2a-c. Paracythere cornuta ULRICH & BASSLER, 19 32, Tennessee Div. Geol. Bull. 38, pi. 27, fig. 13. Graphiadactyllis tenuis COOPER, 1941, Illinois Geol. Survey Re pt. Inv. 77, p. 45, pi. 9, figs. 7-8; SWAIN, 1953, Jour. Paleontology, v. 27, p. 271. Diagnosis . - This species can be recognized by its unique outline, the pattern of fingerprint-like riblets, and especially by its postero-dorsal spine. Remarks . - Bassler and Kellett (19 34, p. 321) erroneously included this species with Graphiadactyllis arkansana (Girty) which has a slightly different surface pattern and possesses no postero-dorsal spine. Ulrich and Bassler {in Bassler, 1932) overlooked Harlton's (1929) previous work and proposed Paracythere cornuta. Morey (1936) used Ulrich and Bassler's species name P. cornuta for specimens from the Chouteau Formation of Missouri that we believe are referable to a new species. Cooper (1941, p. 45) proposed a new species, G. tenuis, erected on specimens from Fayetteville Shale of Oklahoma and in- cluded in his synonomy Harlton's (1929) species B. fayetteui I lens is and the holotype of Kirkbya lindahli arkansana Girty (Roundy, 1926, pi. 1, figs. 14a-c), later selected by Roth (1929, p. 10) as the type species for his new genus OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 21 Graphiadactyllis. We believe that G. fayettev il lens is (Harlton) is a valid species and holds priority over G. tenuis. Stratigraphic occurrence . - Identified from the Springville Shale (State Pond Member) and Chouteau Limestone of Illinois, the Fayetteville Shale (Ches- ter) of Oklahoma and Arkansas, and the Ridgetop Shale of Tennessee. Material studied . - Eighteen specimens were identified and are reposited under catalog numbers 9P43, 9P44 (figured specimens) and 9P45 (all other spec- imens) . GRAPHIADACTYLLIS FERNGLENENSIS Benson, Plate 3, figures 11, 12 1955 Graphiadactyllis fernilenensis BENSON, 1955, Jour. Paleontology, v. 29, p. 1033, pi. 108, figs. 5, 11, 13, 15-17. Diagnosis . - This species can be distinguished from others of its genus by its large size and subreticulate surface pattern. Remarks . - Since the original description of this species was published (Benson, 1955), many better preserved specimens, which show the internal features and some new external ones, have been found in the Springville Shale. The adductor muscle scar is circular and reflects through the carapace wall as a smooth spot in an otherwise subreticulate exterior surface. The hinge is composed of a bar with two crenulate teeth on either end in the right valve, with complementary structures in the left valve. The selvage of the right valve ap- pears to be set inside that of the left valve, but there is no general valve over- lap. The right valve was not described originally and is quite different in lateral outline from the left. The right valve is smaller with a broadly arched dorsum, a long antero-dorsal slope and a slight concavity in the venter. Some specimens found were 2. 10 mm. long, and 1. 13 mm. high. Stratigraphic occurrence . - Origin- ally described from the Fern Glen For- mation and here reported from the Spring- ville Formation (State Pond Member), both lower Osage. Material studied . - Very abundant; more than 100 specimens found. Repos- ited under catalog numbers 9P46, 9P47 (figured specimens) and 9P48 (all other specimens). anterior muscle scar antero-ventral spines Fig. 12. - Lateral view of left valve of Graphiadactyllis fernilenensis Benson showing reticulate surface pattern surrounding circular muscle scar area and small antero-ventral spines on the free margin. X40. GRAPHIADACTYLLIS MORIDGEI Benson, 1955 Plate 2, figures 1-4; plate 3, figure 5 Graphiadactyllis moridiei BENSON, 1955, Jour. Paleontology, v. 29, p. 1035, pi. 108, figs. 1-2. Diagnosis . - This species can be recognized by its long slim outline, small spines on the anterior margin and postero-venter, and a fingerprint-like riblet design. 22 ILLINOIS STATE GEOLOGICAL SURVEY anterior muscle scar Remarks . - Since publication of the orig- inal description of this species from the Fern Glen Formation of Missouri, many well pre- served examples have been found in the Chou- teau Formation of southern Illinois. Left valves of the species possessing an anterior spine not found in the original study have been found in our collections. Larger specimens, some possessing a small postero-ventral spine, were found in the present study indicating that the cotypes from the Fern Glen are not mature instars. Specimens showing well preserved interiors also were found. In them the an- terior flange is divided into the flange proper and a small ridge that terminates in the an- terior spine. The hinge structure is typical of the genus Graphiadactyllis . The dimensions of the Springville adult instars are: length, 1.28 mm.; height, 0.68 mm.; width, 0.50 mm. Stratigraphic occurrence . - Springville (State Pond Member) and Chouteau Formations from southern Illinois; Fern Glen Formation from Missouri. Material studied . - Twenty-two specimens were examined. Reposited under catalog numbers 9P49-9P54 (figured specimens) and 9P55 (all other speci- mens) . anterior spine Fig. 13. - Interior view of left valve of Graphiadactyllis moridgei Benson showing de- tails of the margin and hinge structure. The muscle scar is also visible. X40. GRAPHIADACTYLLIS GRANOPUNCTATUS (Ulrich & Bassler), 1932 Plate 2, figures 9-11 Paracythere granopunctata ULRICH & BASSLER, 19 32, Tennessee Div. Geol. Bull. 38, pi. 27, fig. 4; BASSLER, 1939, Jour. Washington Acad. Sci., v. 25, p. 409. Graphiadactyllis granopunctata BENSON, 1955, Jour. Paleontology, v. 29, p. 1034, pi. 108, figs. 7, 9, 10, 12. Diagnosis . - This species can be recognized by its granopunctate exterior surface, which has a smooth spot over the region of the muscle scar. Stratigraphic occurrence . - Chouteau and Fern Glen Formations of Mis- souri, Ridgetop Shale of Tennessee, and Hannibal, Chouteau, and Springville (State Pond Member) Formations of southern Illinois. Material studied . - Very abundant; more than 150 specimens found. Re- posited under the catalog numbers 9P5 6-9P58 (figured specimens) and 9P59 (all other specimens). GRAPHIADACTYLLIS aff. G. LINEATUS (Ulrich & Bassler), 1932 Plate 1, figure 3 Barychilina I i neat aULRICti & BASSLER, 1932, [part], Tennessee Div. Geol. Bull. 38, pi. 27, figs. 2, 3; BASSLER, 1939, Jour. Washington Acad. Sci., v. 25, p. 409. ? Graphiodactylus, sp. aff. G. lineatus SWAIN, 195 3, Jour. Paleontology, v. 27, pi. 270, pi. 38, figs, lib, d. OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 23 Graphiadactyllis aff. 1034, pi. 108, G. lineatus BENSON, figs. 3, 4, 6. 1955, Jour. Paleontology, v. 29, p. Remarks . - The specimens from the Springville (State Pond Member) For- mation are very close morphologically to those described from the Fern Glen. Material studied . - Eight specimens were found. Reposited under cata- log numbers 9P60 (figured specimen) and 9P61 (all other specimens). Family Uncertain Genus MAURYELLA Ulrich & Bassler, 19 23 Type species: Mauryella mammillata ULRICH & BASSLER Mauryella ULRICH & BASSLER, 1923, Maryland Geol. Survey, Silurian, p. 316. MAURYELLA MAMMILLATA Ulrich & Bassler, Plate 3, figures 6-8 1923 anterior Diagnosis . - Adult instars of the type species and the genus can be re- cognized primarily by the presence of six rounded nodes, a reticulate surface pattern on a straight hinged, anteriorly swung carapace with a very subdued S2 sulcus. Description . - Although this species has been described by Ulrich and Bassler (1923), certain additional information can be added. Carapace medium to small in size, comparatively fragile, subovate in lateral view, and highly ornamented. Greatest length along the midline; greatest height in the anterior end in mature specimens, more central in others. Hingeline straight, free mar- gin gently curved, skewed toward anterior. Elliptical in dorsal view, varied by the development of nodes. Only single valves found, valve size relation- ships unknown. Outer surface of adult instars ornamented with six nodes, early instars and older but still immature instars have five nodes; sixth node only partially developed at maturity. Slight sulcus previously referred to by Ulrich and Bassler as a subcentral pit is present in adult instar but difficult to observe in the immature forms. Hinge appears to be simple but was not well preserved; other interior structures were obscured by poor preservation. Length of hy- potype, 0.80 mm.; height, 0.50 mm.; approxi- mate width, 0.40 mm. Length of smallest ob- served instar, 0.40 mm.; height, 0.28 mm.; width, 0.25 mm. Remarks . - There is no direct evidence as to why Ulrich and Bassler placed this genus in the family Kirkbiidae. They described it as like Kirkbya but without a false border. None of the Kirkbyan characteristics, such as kirk- byan pit or hinge, were seen and therefore the familial classification of this genus is left in doubt. Stratigraphic occurrence . - Springville (State Pond Member) Formation of Illinois and Ridgetop Shale of Tennessee. sulcus nodes Fig. 14. - Lateral view of left valve of Mauryella mammil- lata Ulrich & Bassler show- ing the six nodes and slight sulcus developed on fully mature specimens. X40. 24 ILLINOIS STATE GEOLOGICAL SURVEY Material studied . - Eleven specimens were studied. Reposited under ca- talog numbers 9P62-9P64 (figured specimens) and 9P65 (all other specimens). Family Uncertain Genus ROUNDYELLA Bradfield, 19 35 Type species: Roundyella simplicissimus (Knight) Roundyella BRADFIELD, 19 35, Bull. Am. Paleontology, v. 22, no. 7 3, p. 66; COOPER, 1946, Illinois Geol. Survey Bull. 70, p. 108. Scabernia BRADFIELD, 1935, ibid., p. 67. ROUNDYELLA MOPACIFA Benson, 1955 Plate 3, figures 1-4 Roundyella mopacifa BENSON, 1955, Jour. Paleontology, v. 29, no. 6, p. 1037, pi. 107, figs. 4-6, 8, 10. Diagnosis . - This species is distinguished from others of its genus by the prominent nodes on both ends of each valve. Remarks . - It is now believed that the holotype of this species described from the Fern Glen Formation (Benson, 1955, p. 1037) was not oriented correctly and the orientation is actually the reverse of that indicated in the original des- cription. In several of the Springville specimens one end is slightly higher than the other. Both ends of the Fern Glen specimen were of equal height. We believe that the higher end should be the anterior. Thus the anterior end is the one with the node near the dorsum, not near the venter as formerly stated. Both ends are of about equal thickness. Stratigraphic occurrence . - Identified from the Fern Glen Formation of Missouri and the Chouteau and Springville (State Pond Member) Formations of southern Illinois. Material studied . - Twenty-four specimens were found. Reposited under catalog numbers 9P66-9P69 (figured specimens) and 9P70 (all other specimens). Genus ROUNDYELLA ? Sp. Plate 3, figures 9, 10 Description . - Carapace small, subrectangular in lateral view; oblong in dorsal and anterior views. Straight hingeline, broadly arched venter and rounded ends, surface reticulate with four large nodes protruding from the four corners as viewed from the side. Length of figured specimen, 0.43 mm.; height, 0.25 mm.; width, 0.23 mm . Remarks . - Several interesting specimens were found during this study that deserve comment even though they are not common enough nor well enough understood at this time to warrant establishing a species. The genus Roundyella Bradfield (19 35) was not originally proposed to include species having nodes on the exterior surface, and for this reason, R- mopacifa Benson (1955), which has two nodes, was placed in this genus with some hesitation. Although the speci- mens from the Springville that we refer to Roundyella ? sp. may not be mature, they appear to represent a species that has four nodes and that may be a link between the genera Mauryella and Roundyella, both of which at present have poorly understood family relationships. Early instars of Mauryella have five nodes, whereas these specimens are of slightly different outline and have only four nodes. OSTRACODE FAUNAS FROM SOUTHERN ILLINOIS 25 Material studied . - Nine specimens found. Reposited under catalog num- bers 9P71, 9P72 (figured specimens) and 9P73 (all other specimens). REFERENCES BASSLER, R. S., 1932, The stratigraphy of the Central Basin of Tennessee: Tennessee Div. Geol. Bull. 38, p. 1-268, pis. 1-49. BASSLER, R. S., 1935, Descriptions of Paleozoic fossils from the Central Basin of Tennessee: Washington Acad. Sci. Jour., v. 25, p. 403-409. BASSLER, R. S., and KELLETT, BETTY, 1934, Bibliographic index of Paleozoic ostracoda: Geol. Soc. America Spec. Paper No. 1. BENSON, R. H., 1955, Ostracodes from the type section of the Fern Glen For- mation: Jour. Paleontology, v. 29, p. 1030-1039. BRADFIELD, H. H., 1935, Pennsylvanian ostracoda of the Ardmore Basin, Oklahoma: Bull. Am. Paleontology, v. 22, no. 73, pis. 1-13. BRAYER, R. C., 1952, Salem ostracoda of Missouri: Jour. Paleontology, v. 26, p. 162-174. COLLINSON, CHARLES, and SCOTT, ALAN J. , 1958, Age of the Springville Shale (Mississippian) of southern Illinois: Illinois Geol. Survey Circ. 254. COOPER, C. L. , 1946, Pennsylvanian ostracodes of Illinois: Illinois Geol. Survey Bull. 70, p. 1-177, pis. 1-21. CORYELL, H. N. , and MALKIN, D. S., 1936, Some Hamilton ostracodes from Arkona, Ontario: Am. Mus. Novitates, no. 891, p. 1-20. ECHOLS, D. J., and GOUTY, J. J., 1956, Fern Glen (Mississippian) ostracoda: Jour. Paleontology, v. 30, p. 1315-1323. GEIS, H. L., 1932, Some ostracodes from the Salem Limestone of Indiana: Jour. Paleontology, v. 6, p. 149-188. HARLTON, B. L., 1929, Some upper Mississippian (Fayetteville) and lower Pennsylvanian (Wapanucka -Morrow) ostracoda of Oklahoma and Arkansas: Am. Jour. Sci., ser. 5, v. 18, p. 254-270, pis. 1, 2. MOREY, P. S., 1935, Ostracoda from the basal Mississippian sandstone in central Missouri: Jour. Paleontology, v. 9, p. 316-326, pi. 28. MOREY, P. S., 1936, Ostracoda from the Chouteau Formation of Missouri: Jour. Paleontology, v. 10, p. 114-122, pi. 17. ROTH, ROBERT, 19 29, A revision of the ostracod genus Kirkbya and subgenus Amphissites: Wagner Free Inst. Sci. Publ. 1, p. 1-55. ROUNDY, P. V., 1926, Mississippian formations of San Saba County, Texas; Introduction: The micro-fauna: U. S. Geol. Survey Prof. Paper 146, p. 1-2, 5-23, pis. 1-4. 26 ILLINOIS STATE GEOLOGICAL SURVEY SAVAGE, T. E., 1920, The Devonian Formations of Illinois: Am. Jour. Sci., ser. 4, v. 49, p. 169-182. SWARTZ, F. M., and ORIEL, S. S., 1948, Ostracoda from the Middle Devonian Windon beds in western New York: Jour. Paleontology, v. 22, p. 541. ULRICH, E. O., and BASSLER, R. S., 1923, Silurian: Maryland Geol. Survey, p. 316. WELLER, J. M., etal., 1948, Correlation of Mississippian formations of North America; Geol. Soc. America Bull., v. 52, p. 91-19 6. WELLER, J. M., and SUTTON, A. H. , 1940, Mississippian border of eastern interior basin: Illinois Geol. Survey Rept. Inv. 62, p. 765-858. Illinois State Geological Survey Circular 255 26 p., 4 pis., 14 text figs., 2 tables, July 1958 mmnni CIRCULAR 255 ILLINOIS STATE GEOLOGICAL SURVEY URBANA "♦llr* lM