R- ungenhom STATE OF ILLINOIS William G. Stratton, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Vera M. Binks, Director 1958 CONODONTS from the GLEN DEAN FORMATION (CHESTER) of the ILLINOIS BASIN Carl 6. Rexroad REPORT OF INVESTIGATIONS 209 ILLINOIS STATE GEOLOGICAL SURVEY JOHN C. FRYE. Chief URBANA, ILLINOIS CONODONTS from the GLEN DEAN FORMATION (CHESTER) of the ILLINOIS BASIN Carl B. Rexroad Illinois State Geological Survey Report of Investigations 209 Urbana, Illinois June 1958 PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS STATE OF ILLINOIS HON. WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. VERA M. BINKS, Director BOARD OF NATURAL RESOURCES AND CONSERVATION Hon. Vera M. Binks, Chairman W. H. Newhouse, Ph.D., Geology Roger Adams, Ph.D., D.Sc, Ll.D., Chemistry Robert H. Anderson, B.S., Engineering A. E. Emerson, Ph.D., Biology Lewis H. Tiffany, Ph.D., Pd.D., Forestry Dean W. L. Everitt, E.E., Ph.D., University of Illinois President Delyte W. Morris, Ph.D., Southern Illinois University GEOLOGICAL SURVEY DIVISION JOHN C. FRYE, Ph.D., D.Sc, Chief (76887—2,500—3-58) STATE GEOLOGICAL SURVEY DIVISION Urbana, Illinois. FULL TIME STAFF M. Enid Townley, M.S., Geologist and Assistant to the Chief JOHN C. FRYE, Ph.D., D.Sc, Chief M. Leighton, Ph.D., D.Sc, Chief Emeritus Helen E. McMorris, Secretary to the Chief Velda a, Millard, Junior Assistant to the Chief GEOLOGICAL GROUP M. L. Thompson, Ph.D., Principal Geologist Arthur Bevan, Ph.D., D.Sc, Principal Geologist, Emeritus Frances H. Alsterlund, A.B., Research Assistant ^ M.S., Geologist and Read Ph.D., Senior Geologist and Head, COAL Jack A. Simon, G. H. Cady, Em,firitus Robert M. Kosanke, Ph.D., Geologist John A. Harrison, M.S., Associate Geologist Paul Edwin Potter, Ph.D., Associate Geologist (on leave) William H. Smith, M.S., Associate Geologist Kenneth E. Clegg, M.S., Assistant Geologist Margaret A. Parker, M.S., Assistant Geologist David L. Reinertsen, A.M., Assistant Geologist OIL AND GAS A. H. Bell, Ph.D., Geologist and Head Virginia Kline, Ph.D., Associate Geologist Lester L. Whiting, B.A., Associate Geologist Wayne F. Meents, Associate Geological Engineer Margaret O. Oros, B.A., Assistant Geologist Thomas W. Smoot, M.S., Assistant Geologist Jacob Van Den Berg, M.S., Assistant Geologist Ronald A. Younker, B.S., Research Assistant JuTTA L Anderson, Technical Assistant PETROLEUM ENGINEERING Carl W. Sherman, M.S., Petroleum Engineer and Head INDUSTRIAL MINERALS J. E. Lamar, B.S., Geologist and Head Donald L. Graf, Ph.D., Geologist James C. Bradbury, A.M., Associate Geologist James W. Baxter, M.S., Assistant Geologist Meredith E. Ostrom, M.S., Assistant Geologist PHYSICS R. J. Piersol, Ph.D., Physicist, Emeritus CLAY RESOURCES AND CLAY MINERAL TECHNOLOGY Ralph E. Grim, Ph.D., Consulting Clay Mineralogist W. Arthur White, Ph.D., Geologist Herbert D. Glass, Ph.D., Associate Geologist Walter E. Parham, M.S., Assistant Geologist GROUNDWATER GEOLOGY AND GEOPHYSI- CAL EXPLORATION George B. Maxey, Ph.D., Geologist and Head Merlyn B. Buhle, M.S., Geologist Robert E. Bergstrom, Ph.D., Associate Geologist James E. Hackett, M.S., Associate Geologist John P. Kempton, M.A., Assistant Geologist Wayne A. Pryor, M.S., Assistant Geologist LiDiA Selkregg, D.Nat.Sci., Assistant Geologist Grover H. Emrich, M.S., Research Assistant Lowell A. Reed, B.S., Research Assistant Margaret J. Castle, Assistant Gsologic Draftsman (on leave) ENGINEERING GEOLOGY AND TOPOGRAPHIC MAPPING George E. Ekblaw, Ph.D., Geologist and Head William C. Smith, M.A., Assistant Geologist STRATIGRAPHY AND AREAL GEOLOGY H. B. WiLLMAN, Ph.D., Geologist and Head Elwood Atherton, Ph.D., Geologist David H. Swann, Ph.D., Geologist Charles W. Collinson, Ph.D., Associate Geologist John A. Brophy, M.S., Assistant Geologist T. C. Buschbach, M.S., Assistant Geologist F. L. Doyle, M.S., Assistant Geologist Alan J. Scott, B.S., Research Assistant Robert W. Frame, Supervisory Technical Assistant Romayne S. Ziroli, Technical Assistant Joseph F. Howard, Assistant CHEMICAL GROUP Grace C. Finger, B.S., Research Assistant COAL CHEMISTRY G. R. Yohe, Ph.D., Chemist and Head Thomas P. Maher, B.S., Special Associate Chemist Joseph M. Harris, B.A., Research Assistant PHYSICAL CHEMISTRY J. S. Machin, Ph.D., Chemist and Head Jose M. Serratosa, Dr.Sc, Special Associate Chemist Neil F. Shimp, Ph.D., Associate Chemist Daniel L. Deadmore, M.S., Assistant Chemist JuANiTA Witters, M.S., Assistant Physicist FLUORINE CHEMISTRY G. C. Finger, Ph.D., Chemist and Head Laurence D. Starr, Ph.D., Associate Chemist Donald R. Dickerson, B.S., Special Assistant Chemist Richard H. Shiley, B.S., Research Assistant Raymond H. White, B.S., Special Research Assistant X-RAY W. F. Bradley, Ph.D., Chemist and Head CHEMICAL ENGINEERING H. W. Jackman, M.S.E., Chemical Engineer and Head R. J. Helfinstine, M.S., Mechanical and Adminis- trative Engineer B. J. Greenwood, B.S., Mechanical Engineer Robert L. Eissler, M.S., Assistant Chemical Engineer James C. McCullough, Research Associate (on leave) Walter E. Cooper, Technical Assistant Edward A. Schaede, Technical Assistant ANALYTICAL CHEMISTRY O. W. Rees, Ph.D., Chemist and Head L. D. McVicker, B.S., Chemist Emile D. Pierron, M.S., Associate Chemist William J. Armon, M.S., Assistant Chemist Francis A. Cooltcan, B.S., Assistant Chemist Effie E. Hetishee, B.S., Research Assistant Mary Ann Miller, B.S., Research Assistant Louise J. Porter, A.B., Research Assistant IsTVAN Pusztaszeri, Research Assistant George R. James, Technical Assistant Benjamin F. Manley, Technical Assistant MINERAL ECONOMICS GROUP W. H. VosKuiL, Ph.D., Principal Mineral Economist Hubert E. Risser, Ph.D., Mineral Economist W. L. BuscH, A.B., Associate Mineral Economist ADMINISTRATIVE GROUP EDUCATIONAL EXTENSION George M. Wilson, M.S., Geologist and Head Ira E. Odom, B.A., Research Assistant Shirley Trueblood, B.S., Research Assistant GENERAL SCIENTIFIC INFORMATION Arlene Green, Technical Assistant Del Marie Rogers, B.A., Technical Assistant PUBLICATIONS Dorothy E. Rose, B.S., Technical Editor Meredith M. Calkins, Geologic Draftsman Betty M. Lynch, B.Ed., Assistant Technical Editor Donna R. Wilson, Assistant Geologic Draftsman MINERAL RESOURCE RECORDS Vivian Gordon, Head Betty J. Hanagan, M.S., Technical Assistant Hannah Fisher, Technical Assistant Rosalie Pritchard, Technical Assistant Helen Ross, B.A., Technical Assistant Yvonne M. Sather, Technical Assistant Barbara L. Scott, 6. A., Technical Assistant Elizabeth Speer, Technical Assistant Carolyn Verret, Technical Assistant TECHNICAL RECORDS Berenice Reed, Supervisory Technical Assistant Judith Flach, Technical Assistant Miriam Hatch, Technical Assistant LIBRARY Olive B. Ruehe, B.S., Geological Librarian Beverly Ann Ohren, B.S., Technical Assistant FINANCIAL RECORDS Velda a. Millard, In Charge Eleanor A. Drabik, B.A., Clerk IV Virginia C. Sanderson, B.S., Clerk-Typist III Carolyn S. Toppe, Clerk-Typist II Patricia A. Northrup, Clerk-Typist I * Divided time Topographic mapping- in cooperation with the United States Geological Survey March L 1958 SPECIAL TECHNICAL SERVICES William Dale Farris, Research Associate Beulah M. Unfer, Technical Assistant A. W. Gotstein, Research Associate Glenn G. Poor, Research Associate* Gilbert L. Tinberg, Technical Assistant Wayne W. Nofftz, Supervisory Technical Assistant DoNovoN M. Watkins, Technical Assistant Mary Cecil, Supervisory Technical Assistant Ruby D. Prison, Technical Assistant CLERICAL SERVICES Mary M. Sullivan, Clerk-Stenographer III Rita J. Nortrup, Clerk-Stenographer II Lillian W. Powers, Clerk- Stenographer II Marilyn Bevill, Clerk- Stenographer I Barbara A. Carling, Clerk- Stenographer I Marilyn Scott, Clerk- Stenographer I Edna M. Yeargin, Clerk-Stenographer I Laurel F. Griffin, Clerk-Typist I Ann Vriner, Clerk-Typist I William L. Mathis, Messenger-Clerk II Joseph R. Evans, Messenger-Clerk I AUTOMOTIVE SERVICE Glenn G. Poor, In Charge* Robert O. Ellis, Automotive Shop Foreman David B. Cooley, Automotive Mechanic Everette Edwards, Automotive Mechanic RESEARCH AFFILIATES J Harlen Bretz, Ph.D., University of Chicago Stanley E. Harris, Jr., Ph.D., Southern Illinois University M. M. Leighton, Ph.D., D.Sc, Research Pro- fessional Scientist^ State Geological Survey A. Byron Leonard, Ph.D., University of Kansas Carl B. Rexroad, Ph.D., Texas Technological College Walter D. Rose, B.S., University of Illinois Paul R. Shaffer, Ph.D., University of Illinois Harold R. Wanless, Ph.D., University of Illinois Paul A. Witherspoon, Ph.D., University of Cali- fornia CONSULTANTS George W. White, Ph.D., University of Illinois Ralph E. Grim, Ph.D., University of Illinois CONTENTS Page Introduction 7 Purpose and scope 7 Methods of study 7 Acknowledgments 8 Stratigraphic summary 8 Conodont fauna 9 Abundance of the fauna . 11 Stratigraphic implications of the fauna 11 Uniformity of the Glen Dean fauna 12 Southern faunal province 14 Conclusions 15 Systematic descriptions 15 Genus Cavusgnathus 16 Cavusgnathus convexa Rexroad 16 Cavusgnathus cristnta^YdinsGn 3.ndM.e\v\ 16 Cavusgnathus unicornis Youngquist and Miller 17 Genus Gnathodus 17 Gnathodus modocensis Rexroad . 17 Gnathodus ? sd 18 Genus Hibbardella 18 Hibbardella milleri Rexroad, n. sp 18 Hibbardella ortha Rexroad, n. sp 18 Genus Hindeodella 19 Hindeode/la spp 19 Genus Kladognathus 19 Kladognathus mehli (Rexroad) 19 Kladognathus prima (Rexroad) 19 Genus Lambdagnathus 19 Lambdagnathus fragilidens Rexroad, n. sp 20 Genus Ligonodina 21 Ligonodina hamata Rexroad 21 Ligonodina obunca Rexroad 21 Ligonodina roundyi Hass 21 Genus Lonchodina 22 Lonchodina furnishi Rexroad, n. sp 22 Lonchodina paraclaviger Rexroad, n. sp 22 Lonchodina cf. L. paraclarki Hass 22 Genus Neoprioniodus 23 Neoprioniodus camurus Rexroad 23 Neoprioniodus loxus Rexroad 23 Neoprioniodus scitulus (Branson and Mehl) 23 Neoprioniodus varians (Branson and Mehl) 24 Genus Ozarkodina 24 Ozarkodina compressa Rexroad 24 Ozarkodina curvata Rexroad, n. sp 24 Genus Spatho gnathodus 25 Spathognathodus campbelli Rexroad 25 Spathognathodus cristula Youngquist and Miller 25 Spathognathodus spiculus Youngquist and Miller 25 Spathognathodus cf. S. commutatus Branson and Mehl 26 Genus Roundya 26 Roundya costata Rexroad, n. sp 26 Genus Trichonodella 26 Trichonodella imperfecta Rexroad 26 Genus Indeterminate . 26 References 27 ILLUSTRATIONS Text Figures Page 1. Localities from which conodonts were collected . 8 2. Reily Lake North, locality 1 8 3. Coles Mill, locality 2 9 4. Grassy Knob, locality 3 9 5. Vienna South, locality 4 11 6. Harris Creek, locality 5 .- 11 7. Walches Cut, locality 6 12 8. Gary Brothers Quarry, locality 8 13 9. Brownsville Southeast, locality 9 13 10. Type Glen Dean, locality 10 14 11. Lutgring and Sons Quarry, locality 11 14 12. Mulzer Brothers Quarry, locality 12 15 13. Gerkin Quarry, locality 13 16 14. Diagrammatic reconstruction of a mature representative oi Lambdagnathus Rexroad, n. gen 20 Plates Facing Page 1. Glen Dean conodonts 12 2. Glen Dean conodonts 13 3. Glen Dean conodonts 14 4. Glen Dean conodonts 15 5. Glen Dean conodonts 16 6. Glen Dean conodonts. . 17 CONODONTS FROM THE GLEN DEAN FORMATION (CHESTER) OF THE ILLINOIS BASIN CARL B. REXROAD ABSTRACT The conodont fauna of the Glen Dean Formation in its outcrop area around the margin of the Illinois Basin is described. Samples were collected from thirteen uniformly spaced sections in southern Illinois, Indiana, and Kentucky, including the type section, and virtually every sample from limestone and many from shale yielded conodonts. Twenty-seven species, seven new, were recognized and are referable to thirteen genera: Cavusgnathus, Gnathodus, Hibbardella, Hindeodella, Kladognathus (new name for Cladognathus), Ligonodina, Lonchodina, Neoprioniodus, Ozarkodina, Roundya, Spathog- nathodus, Trichonodella, and one new genus Lambdagnathus. The fauna is unaffected by iithologic variations and is remarkably uniform geo- graphically, although a southern faunal province based on abundance of certain species is recognized. Six species appear restricted to the formation but their ranges cannot be considered fixed because the remainder of the Chester Series has not been sampled in comparable detail. INTRODUCTION Purpose and Scope Studies of conodonts from the Chester Series in the type area of southwestern IIH- nois (Rexroad, 1957) showed a diversified fauna from eight formations and indicated that conodonts will be useful in strati- graphic investigations of Chester strata. Although the earlier study established the Chester conodont fauna as a whole, that study was confined to one area and mainly to the shale beds. Thus it did not allow evaluation of limestone faunas, effects of facies changes, nor faunal variations within a single formation over a broad area. Such details, along with the more precise delim- iting of stratigraphic ranges within the se- ries, were the objectives of the present study. The Glen Dean Formation was chosen for study because: (1) it contains relatively abundant conodonts in the type area of the Chester Series; (2) it is well exposed around the margin of the Illinois Basin; (3) in much of its outcrop area it consists of a lower massive limestone unit and an upper unit of mixed lithology, dominantly shale, which would be desirable for facies analysis; and (4) its position in the middle Chester might show whether several species, which in the initial study appeared to have a range limited to the lower or to the upper part of the series, are truly restricted. Thirteen sections from Illinois, Indiana, and western Kentucky, including the type section of the formation, were sampled. Only sections where stratigraphic positions are well established were chosen as collect- ing localities and these were spaced as uni- formly as was consistent with the choice of complete or nearly complete Glen Dean sections. Methods of Study From each exposure, channel samples of all lithologies except sandstone were col- lected. The thickness represented by each sample was commonly one or two feet but depended upon the thickness of the Iitho- logic units. Initial samples averaged about 700 grams. The samples were processed, then bulk samples were collected from each zone that contained abundant conodonts. In addition, a sample of approximately 150 pounds of crushed rock was collected from the lower massive limestone unit in the Mulzer Brothers quarry, location 12. [7] ILLINOIS STATE GEOLOGICAL SURVEY In the laboratory the limestone samples were crushed to less than 5/^-inch size and dissolved in 10 percent acetic acid. Shales were dissociated by boiling and by the use of the Campbell microfossil washing ma- chine. Residues were screened and the por- tion retained between the 20- and 100-mesh screens was concentrated by gravity sep- aration in tetrabromoethane. Specimens picked from the heavy residues were grouped, first by sample and location num- ber, then regrouped by genus and species. Acknowledgments The project was directed by C. W. Collin- son. D. H. Swann selected sections to be sampled in Illinois and gave helpful advice on the stratigraphic aspects of the study. Discussions of taxonomy with A. J. Scott proved most helpful. Valuable criticism of the manuscript was given by C. W. Collin- son, D. H. Swann, and H. B. Willman. Marie Litterer prepared the text figures. Edmund Nosow of the Kentucky Geolog- ical Survey collected samples from two sec- tions in Kentucky (localities 7 and 8) and provided information about them. Ned Smith of the Indiana Geological Survey aided in the selection of suitable outcrops in Indiana. A manuscript by T. G. Perry Fig. 1. — Localities from which conodonts were col- lected. See outcrop diagrams (figs. 2-13) for detailed descriptions. LOG. I-REILY LAKE NORTH NORTH QUARRY Limestone, gray, medium to coarse, shaly, very shaly and fossiliferous toward base 20' Shale, gray, soft, fossiliferous 5'6" Limestone, coarse, fossiliferous. 2' Limestone, gray,weathers\ buff, nodular, stialy. 2'6" Limestone, ligtit gray, coarse, fragmental, with) I'to 4' gray fossiliferous stiale bed. 12' to 17' Stiale, gray, fossil., 6" dork limestone lentil near top 3'6" Limestone, gray, fossiliferous 4 Fig. 2. — Reily Lake North, locality 1. Small quarry in Mississippi Valley bluff about 1.1 miles northwest of Reily Lake, SEi/4 SE14 sec. 24 (ex- tended), T. 6 S., R. 8 W., Chester quadrangle, Randolph County, Illinois. and Ned Smith gave additional information about the Glen Dean Formation in Indi- ana. A. K. Miller loaned Pella Beds mate- rial from the State University of Iowa re- pository, P. E. Cloud and W. H. Hass loaned Barnett Formation type specimens from the U. S. National Museum, and M. G. Mehl of the University of Missouri made available figured specimens from the Caney Shale. STRATIGRAPHIC SUMMARY The Glen Dean Formation, although highly variable in lithology, is a well de- fined unit in its extensive outcrop area around the southwestern, southern, and southeastern margin of the Illinois basin and in the subsurface within the basin. It overlies the Hardinsburg Formation with apparent conformity and is overlain by the Tar Springs Sandstone, unconformably in GLEN DEAN CONODONTS L0C.2-C0LES MILL 1 Sandstone, brown, fine 6'-7' /.■. to Shale, gray to dark gray, sandy. 2'6" J-t^. ^29 z: < UJ Q LJ _J Br ^^ 5 23 limestone' near middfe. 5'6" y_^^^_ f \^\^ 1 h-'"^ /I'll, 9- y / 1 1 1 , 1 &• /l III s -^ Shale, qrav. poorlv / 5 ? laminatea. -^/'^ \^^\ " 1" Limestone, gray, crinoidal, /| o | o |^o oolitic, cross- bedded, /-^» | o | o |o now covered. 8' /o | c | ^o | o o Fig. 3. — Coles Mill, locality 2. Just above mouth of ravine, east of flour mill at south edge of Ches- ter, W. line NWi/4 sec. 30, T. 7 S., R. 6 W., Chester quadrangle, Randolph County, Illinois. some areas but apparently conformably in others. Although the Glen Dean is the up- permost formation of the middle Chester, it is nearly in the middle of the series, as eight of the sixteen formations of the stand- ard sequence overlie it. The lithologic sequence of twelve of the thirteen sections sampled is shown in text figures 2-13. Samples which contain cono- donts are shown in solid black. The sec- tions selected over-emphasize the amount of limestone in the formation because the dominantly limestone sections tend to be better exposed than those composed largely of shale. Generally in Indiana and Ken- tucky a "lower massive limestone" is rec- ognized and above that a unit of mixed lith- ology in which shales predominate but in which limestones and sandstones are pres- ent. This twofold division does not persist in the Illinois outcrop belt, however, and there are places where shale predominates in the lower part and limestone in the up- per. The lower massive limestone, although persistent over much of the outcrop, varies in lithology and may be crinoidal, oolitic, dolomitic, or siliceous. Generally it occurs in beds one to two feet thick and is medium to dark gray, medium- to coarse-grained, ar- gillaceous limestone with crystallinity that LOG. 3 -GRASSY KNOB Sandstone, reddish-brown, thm bedded. 4' & Covered 2 3 Limestone, dork gray, granular crinoidal 4' :^s: Covered, I0'6" Limestone, gray, oolitic 3 f°l ° I Covered 3'6" Limestone, dork gray, oolit iL-ffii Covered. 10' Limestone, gray, crinoidal. 3' r ^^^ Covered. 4' Limestone, gray, medium- to coarse-grained, crinoidal. Hardinsburg shale approx. 5' below base of section. 15' .1.1.1 I I I I rrm YTTA LZL 1 r Fig. 4. — Grassy Knob, locality 3. Stream bed in picnic area NEi/^ SEi^ sec. 27, T. 10 S., R. 3 W., Alto Pass quadrangle, Jackson County, Illinois. is caused in large part by abundant fos- sil fragments. The upper unit of the for- mation in Indiana and Kentucky is highly variable and contains shales, limestones, and sandstones. Some of the upper beds vary several feet in thickness, and may even thin out, within a single quarry. CONODONT FAUNA Conodonts in considerable variety are present in all of the thirteen Glen Dean sections sampled (table 1). Twenty-seven species belonging in twelve genera, one new, were identified, and specimens of a thirteenth genus, Hindeodella, are abun- dant. Also present are numerous fragments which apparently represent a new genus but which are not sufficiently well pre- served to warrant detailed description. Of the twenty-seven species, seven are new. 10 ILLINOIS STATE GEOLOGICAL SURVEY Table 1. — Geographic Occurrence of Conodont Species Locality numbers refer to outcrops shown in text-figure 1 and described in detail by text-figures 2-13. U and L refer to upper Glen Dean and lower Glen Dean, respectively. LOCALITY 1 2 3 4 5 6L 6U 7L 8U 9L 9U lOL IIL 11U12L 12U 13L Cavusgnathus — — — — — — — — — — x — — — — — — C. convexa x x x x x— — x — — — x x — x x x C. cristata x x x x x — — x x x — x x x x x x C. unicornis xxxxxxxxxx — -xxxxxx Gnathodus G. modocensis ......x — x — x x — x x x — x x — x — x G. ?sp — — — — X — — — X — — — — — — — — Hibbardella H. milleri xxxxxx — xxx — xxxx — x H. ortha x x x — x — — — x — — x — — x x x Hindeodella xxxxxxxxxxxxxxx xx KJadognathus — — — x — — — — — x — x x x — — x K. prima x x x — x — — — — x — — — — — __ K. mehli — x — — — — — — — — — — — — — — — Lambdagnathus — — x — — — — x x x— — x x — — — L. fragilidens x x — — x — — — — — — x — — x — x Ligonodina L. hamata xxxxxx — xxx — xxxx xx L. obunca xxxxx — — xxx — xxxx xx L. roundyi x — x — — x — x — — — — x — x — x Lonchodina . . . . — — — — — — — x — — — — — x — — — L. furnishi x — x — x — — — x — — — — — x — x L. paraclaviger — — x — — — — — — — — — x — x — x L. cf. paraclarki — — — — — — — — — — — — x — x — x Neoprioniodus N. camurus x x — — — — x — — x N. loxus X X X — — — — — X — N. scitulus xxxxxxxxxx- N. varians x x x — x — — — x x- Ozarkodina O. compressa x x x x x x — x x x O. curvata x x — — — — — — — x Roundya R. costata x — — — — — — x — x X X — X X X X X — X — X X X X X X X X X X X X X X X X X X X — X — X — • X Spathognathodus . S. campbelli — x — — — — — — — — — — — — S. cf. commutatus — — — — x — — x x — — x — — S. cristula x x — x — — — — — x x x x x S. spiculus X X — X — — — — — — — X — X Trichonodella T. imperfecta — x — — — — — — — — — — x — Genus indet x GLEN DEAN CONODONTS 11 L0C.4- VIENNA SOUTH Shale, buff, sandy, micaceous. 6 Limestone, gray, brown and red sandy and sholey, fossil. 9' Limestone, ligtit to dork gray, medium to coarse-grained, port crinoidal, part oolitic, variable laterally. Contact with Hardinsburg shale approximately 3' below base of this section. 26' o Fig. 5. — Vienna South, locality 4. Abandoned quarry, west side of Highway 45, about 1.4 miles south of junction of Highways 45 and 165 in Vienna, SE14 SEi/4 sec. 8, T. 13 S., R. 3 E., Vienna quad- rangle, Johnson County, Illinois. These are Hibhardella milleri, H. ortha, Lamhdagnathus jragilidens, Lonchodina furnishi, L. paraclaviger , Roundya costata, and Ozarkodina curvata. Abundance of the Fauna Conodonts are found in at least moderate abundance at all the outcrops sampled (50 to 150 specimens per 1000 grams of raw sample is considered abundant). Alto- gether more than 4000 specimens were ex- amined and hundreds of representatives of many species were studied. Conodonts were found to be much more abundant in lime- stone than in shale. The most abundant species encountered were Neoprioniodus scitulus and Cavus- gnathus unicornis but they were closely fol- lowed in numbers by Ligonodina obunca and Spathognathodiis cr is tula. Among those also considered abundant are Cavus- gnathus convexa, Ozarkodina compressa, and Spathognathodus spiculus. With the exception of eight rare species, all others listed in table 1 occur commonly, but Cavusgnathus cristata, Gnathodus mo- docensis, Hibhardella milleri, Ligonodina hamata, and Neoprioniodus varians were found in slightly larger numbers than the others. Kladognathus prima, Lambdagna- thus jragilidens, and Lonchodina paraclavi- LOC. 5 -HARRIS CREEK Limestone, gray, coarse-grained, cnnoidal, weathers to thin tan beds 19' Covered interval 6 6 Limestone, dark gray, medium to coarse- grained, crinoidal I4'8" ER Fig. 6. — Harris Creek, locality 5. Hillside above and below abandoned section of road, NW14 NWi^ sec. 15, T. 11 S., R. 9 E., Shawneetown quadrangle, Hardin County, Illinois. ger are very uncommon in the Glen Dean; Gnathodus ? sp., Kladognathus mehli, Lon- chodina furnishi, L. cf. L. paraclarki, Roundya costata, Spathognathodus camp- belli, S. cf. S. commutatus, and Trichono- della imperfecta are considered rare. Stratigraphic Implications of the Fauna Although the 1957 report established the general nature of the conodont fauna of the Chester Series, only one complete sequence was studied and the stratigraphic ranges for species were not well established. Con- sequently, a project to determine precisely the ranges of species in the Chester Series is now in progress. The present study was designed to deter- mine the constancy of a conodont fauna in differing lithologies and over wide dis- tances. However, it has developed impor- tant information about stratigraphic ranges. The lower Chester (Renault and Paint Creek) collections studied in 1957 by Rex- road were large enough (200 or more speci- mens) to be considered truly representative. Comparison of these faunas with those of the middle Chester Glen Dean indicates that several forms, Cavusgnathus characta, Ozarkodina recta, O. ? bella, and Neopri- 12 ILLINOIS STATE GEOLOGICAL SURVEY Fig. 7.— Walches Cut, locality 6. Illinois Central Railroad cut about 1.9 miles E-NE of Scotts- burg. Section illustrated begins about 50 yards east of overpass bridge. Carter coordinates 23-H-21, 4000 feet N. of S. line, 1035 feet E. of W. line of quadrangle H-21, Princeton East quadrangle, Caldwell County, Kentucky. oniodus erectus, appear to be restricted to the lower Chester. Representatives of the genera PoJygnatliiis and Synprioniodina are also restricted to pre-Glen Dean rocks in the type Chester area but must be eval- uated further. Six species have been recorded from only the Glen Dean. Three, Kladognathus mehli, Lonchodina fumishi and Roimdya costata, are uncommon; but the remaining three, Hihhardella ortha, Larnbdagnathus fragili- dens, and Lonchodina poracJaviger, are sufficiently abundant to appear stratigraph- ically significant. Uniformity of the Glen Dean Fauna The over-all uniformity of the conodont fauna is impressive from three standpoints: first, uniformity in differing lithologies; second, uniformity between the lower and upper parts of the formation; and third, geographic uniformity. One important ex- ception to this pattern will be noted later No differences were found in the species represented in collections from differing types of limestone — oolitic, crinoidal, dolo- mitic, and others — nor between various kinds of shale. Conodonts were found to be more abundant and better preserved in LOG. 6 -WALCHES CUT Sandstone, tan, massive. 31' Covered interval. 8' Limestone, gray, thin-bedded, ^ sandy, abundantly fossiliferous. 2'6" Stiale, dark gray, calcareous, with limestone beds, fossiliferous. 9' Sandstone, gray, calcareous, \ fossiliferous. I'-Z' Shale, dark gray 5' Sandstone, gray, thin-bedded upper part calcareous, very fossiliferous; middle shale 5'6" Shale, very dark gray, slightly fossiferous; thin siltstone partings 37' Limestone, gray, massive, medium to coarse-grained. iQi^i" Shale, dark gray. 7 CO o EXPLANATION OF PLATE 1 All figures X 40 Numbers in parentheses after explanations refer to locality and sample numbers, for example (7-4) refers to locality 7, sample 4. Figure 1, 2 Gnathodus modocensis Rexroad; 1, outer lateral view (7-4); 2, oral view (7-14), 3-5 Gnathodus} sp.; 3, inner lateral view (8-7); 4, 5, oral views (8-2 and 8-7). 6-11 Cavusgnathus unicornis Youngquist and Miller; 6, 7, inner and outer lateral views of mature specimens (1-43 and 9-30); 8, 9, oral and inner lateral views of young speci- mens (both 2-6); 10, 11, oral and inner lateral views of an old specimen (1-26). 12-14 Cavusgnathus convexa Rexroad; 12, inner lateral view of mature specimen (1-43); 13, inner lateral view of old specimen (1-61); 14, outer lateral view of mature speci- men (1-47). 15-17 Cavusgnathus cristata Branson and Mehl; 15, inner lateral view (11-18); 16, aboral view (3-2); 17, outer lateral view (9-14). Illinois State Geological Survey R. 1. 209, Plate 1 Rexroad — Glen Dean Conodonts Illinois State Geological Survey R. I. 209, Plate 2 Rexroad — Glen Dean Conodonts GLEN DEAN CONODONTS 13 LOG. 8- GARY BROTHERS QUARRY Covered, some ton limestone ledges exposed. 5' Limestone, ton, massive, coarse grained, partly oolitic. 3' Shale, black, calcareous, fossiliferous Limestone, dark gray, fine to medium-grained. 7' Limestone, gray, fossiliferous, medium to thin-bedded, has thin shale partings. I3'3" Shale parting. 2" Limestone, tan to gray, coarse-grained, partly oolitic, fossiliferous, with thin shale partings. I0'9" Fig. 8. — Gary Brothers Quarry, locality 8. Quarry 2000 feet east of Highway 231, Carter coordi- nates 14-H-35, 1200 feet N. of S. line, 6300 feet E. of W. line of quadrangle H-35, Sugar Grove quadrangle, Butler County, Kentucky. limestone than in shale, but twenty-one of the twenty-seven Glen Dean species are common to both limestone and shale. Kladognathus mehli and Spathognathodus camphelli, the two species limited to shale, w^ere each represented in this study by less than four specimens, these from a single lo- cality. The four species found only in lime- stone probably reflect the method of sam- pling rather than environmental factors. Zones particularly productive of conodonts were resampled in quantity, and, because of the greater abundance of conodonts in limestone than in shale, a disproportion- ately high percentage of specimens are L0G.9- BROWNSVILLE SOUTHEAST Limestone, gray, medium-grained, crinoidol, cross-bedded. 3'6" I Shale, gray and tan, fossiliferous, calcareous, slightly sandy. 4'6" M:: Covered. Limestone, light gray to tan, medium to fine-grained, crinoidol, argillaceous. 9' IZZI I .T I -1:31 rh^^ Limestone, gray, medium to coarse- grained, crinoidol. 24' III III izn Fig. 9. — Brownsville Southeast, locality 9. Mc- lellan Stone Quarry No. 4, just southwest of Highway 65 approximately 3.6 miles from Green River bridge in Brownsville, Carter co- ordinates line between 24-1-40 and 4-H-40, 5450 feet E. of W. line of quadrangle, Rhoda quad- rangle, Edmonson County, Kentucky. from limestone. Ligonodina roundyi and Lonchodina paraclarki have both been re- corded from shale according to Hass's dis- tribution chart (1953, table 1), but in this study Ligonodina roundyi and Lonchodina cf. L. paraclarki were found only in lime- stone. A comparison between the lower Glen Dean massive limestone and the upper Glen Dean zone of mixed lithology shows that twenty-three species are common to both the lower and upper Glen Dean. The two species limited to the upper part are rare, and the two limited to the lower part are EXPLANATION OF PLATE 2 40 All figures X Numbers in parentheses after explanations refer to locality and sample numbers, for example (12-3) refers to locality 12, sample 3. Figure 1-4 5-8 9-12 13-16 Hindeodella spp., lateral views (12-3, 11-15, 2-42 and 11-14 respectively). Roundya costata Rexroad, n.sp.; 5, posterior view of holotype (12-4); 6, lateral view of a paratype (12-11); 7, posterior view of a paratype (13-17); 8, lateral vicAv of a para- type, a young specimen (1-61). Hibhardella ortha Rexroad, n.sp.; 9, lateral view of a paratype, a young specimen (13-3); 10, posterior view of holotype (13-1); 11, posterior view of a paratype, a vari- ant (8-7); 12, posterior view of a paratype, a young specimen (13-3). Hihbardella milleri Rexroad, n.sp.; 13, oblique posterior view of holotype (1-61); 14, lateral view of a paratype, a young specimen (7-16); 15, anterior view of a para- type (10-4); 16, lateral view of a paratype (13-15). 14 ILLINOIS STATE GEOLOGICAL SURVEY LOG. 10- TYPE GLEN DEAN 0) o. e ii Covered /^ z < lij Q liJ -1 CO . . . /5 J'^ Limestone, tannish-gray, medium to 1 |.o qrained, crinoidal. 13' 1 E 1 fitiale, dark grov in uDOer 1-1/2. \^ ' 1 ' dark red and greenisti-gray in middle, J_—^_ and dark gray in lower 2-1/2'. /IE-=_ f\ 1 1 B: zr < lij Q UJ _) CD Limestone, gray, medium- groined, fossiliferous, crinoidal 18' 3" ( 1 1 1 rn 'S { 1 B- 1 1 1 5- 1 1 BliO ' ' B ^ 1 1 Bl 5 1 1 & f 1 1 1 BS^ 1 Fig. 13. — Gerkin Quarry, locality 13. Small aban- doned quarry about 2.9 miles NW of Shoals, NW14 SWi/4 sec. 12, T. 3 N., R. 4 W., Shoals quadrangle, Martin County, Indiana. Genus Cavusgnathus Harris and Hollings- worth, 1933 Type species: Cavusgnathus alta Harris and Hol- lingsworth Cavusgnathus convexa Rexroad Plate I, figures 12-14 Cavusgnathus convexa Rexroad,, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 17, pi. 1, figs. 3-6. The holotype and the two paratypes of this species are from the Glen Dean Forma- tion in the type area of the Chester Series, and specimens from other Glen Dean loca- tions conform closely to the type specimens. The large number of specimens examined in this study show clearly the changes which occurred during ontogeny. Young speci- mens tend to be narrow with nearly straight parapets. With growth they tend to broaden the platform without a proportional in- crease in length, increase the flare of the inner lip of the navel, and some gerontic in- dividuals show additional denticles on the anterior margin of the blade, increasing the number of blade denticles from the typical four, five, or six to as many as nine. Vari- ants which in oral outline show blades less regularly convex than any previously known are also present in the Glen Dean collec- tions. Material studied. — 201 specimens from this study, 35 from Rexroad 1957 study. Distribution. — Renault, Golconda, Glen Dean, Menard, and Kinkaid Formations of Illinois; Glen Dean of Indiana and Ken- tucky. Repository. — Illinois State Geological Survey, 3P1, 3P2, 3P3 (figured specimens). Cavusgnathus cristata Branson and Mehl Plate 1, figures 15-17 Cavusgnathus cristata Branson and Mehl, 1940, Denison University Bull., Jour. Sci. Labs., v. XXXV, p. 177, pi. V, figs. 26-31. Hass, 1953, U. S. Geol. Survey Prof. Paper 243-F, p. 77, pi. 14, figs. 12-14. Cooper^ (part) 1947 Jour. Paleon- tology, V. 21, no. 2, p. 91, pi. 20, figs. 4-6 (not figs. 7-10). Elias, 1956, Petroleum Geology of southern Oklahoma: Am. Assoc. Petrol. Geol., V. 1, p. 115, pi. II, figs. 1-6.? BiscHOFF, 1957, p. 19, pi. 2, figs. 7a, b. Cavusgnathus cristata var. grandis Elias, 1956, Pe- troleum Geology of southern Oklahoma: Am. Assoc. Petrol. Geol., v. 1, p. 115, pi. II, figs. 12-14. Some of the Glen Dean specimens con- form quite closely to Branson and Mehl's holotype of C. cristata, but most have a more regular outline of the oral margin of the blade as viewed laterally, thus resem- bling C. convexa. There are a number of differences, however, between C. convexa and C. cristata. The navel of C. convexa extends to the posterior tip of the specimen and is very asymmetric with greater flare of the inner lip in contrast to the greater sym- metry of the navel of C. cristata which ex- explanation of plate 5 All figures X 40 Numbers in parentheses after explanations refer to locality and sample numbers, for example (12-3) refers to locality 12, sample 3. Figure 1, 2 Genus indeterminate; posterior views (12-3 and 1-40). 3, 4 Neoprioniodus varians (Branson and Mehl); inner lateral views (11-20 and 8-4). 5, 6 Neoprioniodus camurus Rexroad; inner lateral views (12-2 and 12-4). 7-9 Neoprioniodus loxus Rexroad; 7, 8, inner lateral views (1-12 and 13-2); 9, outer lat- eral view (2-22). 10-14 Neoprioniodus scitulus (Branson and Mehl); 10, 11, inner lateral views of young specimens (12-29 and 1-38); 12-14, inner lateral views of mature specimens (1-41, 10-4, and 1-41 respectively). Illinois State Geological Survey R. I. 209, Plate 5 Rexroad — Glen Dean Conodonts Illinois State Geological Survey R. I. 209, Plate 6 Rexroad — Glen Dean Conodonts GLEN DEAN CONODONTS 17 tends only part way to the posterior, leav- ing the posterior fourth of the aboral mar- gin sharp-edged. At the posterior end of the oral trough a median carina is typical in C. cristata but is present only rarely in C. convexa and then consists of only a few isolated nodes. The parapets of C. con- vexa are ornamented by sharper more reg- ularly spaced transverse ridges than those of C. cristata. There is a considerable range in the size of even the mature specimens of C. cris- tata and in the older specimens the trans- verse ridges of the parapets tend to become less sharp and in some cases remain only as a series of nodes. For these reasons, Elias' variety C. cristata var. grandis is not con- sidered valid. Material studied. — 71 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky, Barnett Formation of Texas, and the Delaware Creek Member of the Caney Shale of Okla- homa. Cavusgnathus unicornis Youngquist and Miller Plate 1, figures 6-11 Cavusgnathus unicornis Youngquist and Miller, 1949, Jour. Paleontology, v. 23, no. 6, p. 619, pi. 101, figs. 18-23. Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 17, pi. 1, fig. 7. Cavusgnathus cristata Branson and Mehl, Cooper (part), 1947, Jour. Paleontology, v. 21, no. 2, p. 91, figs. 7-10. This easily recognizable species is an im- portant element of the Glen Dean Forma- tion at all locations studied. Except for changes during ontogeny, the species shows Httle variation. The young specimens tend to be narrow with parapets nearly straight or slightly concave toward the inner side. With growth the platform broadens with- out a proportional increase in length, there develops a pronounced convexity of the in- ner parapet near the posterior as viewed orally, an increase in the flare of the inner lip of the navel, and an increase in the num- ber of small denticles on the blade anterior to the prominent posterior denticle. Material studied. — 524 specimens from this study, 170 from Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indiana, and Kentucky, and the Pella Beds of Iowa. Repository. — Illinois State Geological Survey, 3P7, 3P8, 3P9, 3P10, 3P11 (figured specimens). Genus Gnathodus Pander, 1856 Type species: Gnathodus mosquensis Pander Gnathodus modocensis Rexroad Illinois 1, figs. Plate 1, figures 1 and 2 Gnathodus modocensis Rexroad, 1957, Geol. Survey Rept. Inv. 199, p. 30, pi. 15-17. Most specimens of Gnathodus that occur in the Glen Dean Formation are very uni- form in appearance and may be readily identified as G. modocensis. As stated pre- viously (Rexroad, 1957, p. 30), this species closely resembles G. bilineatus (Roundy). EXPLANATION OF PLATE 6 All figures X 40 Numbers in parentheses after explanations refer to locality and sample numbers, for example (8-7) refers to locality 8, sample 7. Figure 1, 2 Ozarkodina compressa Rexroad; 1, inner lateral view (8-7); 2, outer lateral view (1-25). 3, 4 Spathognathodus cristula Youngquist and Miller; 3, inner lateral view of a mature specimen (2-31); 4, inner lateral view of a young specimen (12-7). 5-7 Spathognathodus spiculus Youngquist and Miller; lateral views (10-3, 10-3, and 1-43 respectively). 8 Spathognathodus cf. S. commutatus Branson and Mehl; inner lateral view (8-7). 9 Spathognathodus campbelli Rexroad; inner lateral view (12-14). 10-16 Lambdagnathus fragilidens Rexroad, n.gen., n.sp.; 10, 11, 13, two oblique views and an oral view of holotype (1-41); 12, outer lateral view of a paratype (1-49); 14, aboral view of a paratype (1-60); 15, 16, posterior views of two paratypes (12-composite and 12-2). 18 ILLINOIS STATE GEOLOGICAL SURVEY This is especially apparent when compar- ing the adult of the former with the young of the latter. This resemblance seems to indicate that the two are closely related al- though not conspecific because of the differ- ences between adults. About five percent of the specimens of Gnathodus found in the Glen Dean bear an especially strong resemblance to G. hilineatus (Roundy). These specimens, nevertheless, are identi- fied as G. modocensis and are considered variants toward the closely related species. Material studied. — 87 specimens. Distribution. — Paint Creek and Glen Dean Formations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P12, 3P13 (figured specimens). Gnathodus ? sp. Plate 1, figures 3-5 Four specimens from two localities are difficult to place generically because they are young and broken. From oral view a free blade continues as a slightly sinuous carina with nearly symmetrical parapet-like units on each side. On the aboral side of the platform is a navel which in the broken specimens gives the impression of being asymmetrical, the inner side being essen- tially limited to the under side of the inner parapet and the outer side perhaps extend- ing outward as a platform beyond the outer parapet-like structure on its oral surface. This development is similar to that in sev- eral species of Gnathodus including G. girtyi Hass from the Barnett Formation of Texas. Material studied. — 4 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P14, 3P15, 3P16 (figured speci- mens). Genus Hibbardella Bassler, 1925 Type species: Hibbardella angulata Hinde Hibbardella milleri Rexroad, n.sp. Plate 2, figures 13-16 Hibbardella n.sp. ? Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 31, pi. 1, fig. 19. Anterior arch moderately deep, charac- teristically with a small central denticle im- mediately anterior to main cusp, each lat- eral bar typically bearing four discrete round denticles bowed posteriorly and in- creasing in size distally, distal ends of bars spatulate; aboral edges of lateral bars thin, grooved, may be slightly sigmoidal as viewed from anterior and meeting at base of cusp in an acute angle, bars inclined 5° to 20° posteriorly; anterior faces convex and inclined posteriorly downward. Cusp large, recurved, elliptical in cross section, sharp edged fore and aft, but increasingly rounded toward tip. Posterior bar short, anterior end of bar stout in adults, longer and thinner in young, few denticles or nodes on oral surface in adults, marked attachment scars on anterior end of bar seen in lateral view; aboral margin wedge- shaped with longitudinal median groove. The species is named in honor of A. K. Miller of the State University of Iowa. Material studied. — 113 specimens from Glen Dean, 25 from Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P17 (holotype), 3P18, 3P19, 3P20 (para types). Hibbardella ortha Rexroad, n.sp. Plate 2, figures 9-12 Anterior arch deep, anterior face coin- ciding with anterior face of main cusp; the two lateral limbs nearly in a common plane, anterior faces flat, each limb typi- cally with five erect primary denticles fused about one-half way to apices, some speci- mens with germ denticles between; aboral edges of lateral limbs thin, meeting at base of cusp at a low obtuse angle. Cusp erect, thin, nearly straight, triangular in cross sec- tion with flat anterior face and a sharp edge posterior. Posterior bar moderately deep, thin, none complete, bears closely spaced, laterally compressed denticles; aboral mar- gin with median longitudinal groove which extends anteriorly to tiny aboral pit near the anterior of base of cusp. GLEN DEAN CONODONTS 19 I do not believe that the partial fusion of the denticles of this species justified the erection of a genus distinct from similar species with discrete denticles. Material studied. — 31 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P21 (holotype), 3P22, 3P23, 3P24 (para types). Genus Hindeodella Bassler, 1925 Type species: Hindeodella suhtilis Ulrich and Bassler Hindeodella spp. Plate 2, figures 1-4 Hindeodella is represented by abundant fragmentary specimens but few complete specimens. Specific references do not seem justified on the basis of the several com- plete specimens and fragments representing only the termini or midsection of bars. Several representative specimens are figured to indicate the nature of the material. Repository. — Illinois State Geological Survey, 3P25, 3P26, 3P27, 3P28 (figured specimens). Genus Kladognathus Rexroad, n. name Type species: Cladognathus prima Rexroad W. H. Hass has called to my attention the fact that the name Cladognathus Rex- road is preoccupied by Cladognathus Bur- meister given to a genus of the Coleoptera (Burmeister, 1847, p. 364). Kladognathus mehli (Rexroad) Plate 3, figure 5 Cladognathus mehli Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 29, pi. 1, figs. 11, 12. Only two additional specimens of this species were found in this study, both from the location from which the holotype was described. They show little variation from the type specimens. Material studied. — 8 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P29 (figured specimen). Kladognathus prima (Rexroad) Plate 3, figure 6 Cladognathus prima Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 28, pi. 1, figs. 8-10. The type and figured specimens show the amount of variation to be expected in this species, but its occurrence is not common enough to allow description of growth stages which probably would clarify the phylogenetic relations of Kladognathus. The chief variation in this species is in the number of denticles of the anterior process and hence in the length of the process. This suggests that the genus developed from Ligonodina. Material studied. — 20 specimens from this study, 10 from Rexroad 1957 study. Distribution — Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indi- ana, and Kentucky. Repository. — Illinois State Geological Survey, 3P30 (figured specimen). Genus Lambdagnathus Rexroad, n.gen. Type species: Lambdagnathus fragilidens Rexroad, n.sp. New genus ?, Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 41, pi. 4, figs. 8-13. Complex unit consisting of a posterior denticulate process and blade-like anterior and inner lateral denticulate processes with an apical denticle, usually triangular in shape, at the juncture of the three, and, aborally, a triangular shaped pit at their juncture (figure 14). The posterior bar is usually the shortest of the three branches, is thin, and aborally bears a median groove as do the other processes. The anterior process may continue nearly in line with the posterior bar or may incline somewhat outward and down, and it may be slightly sinuous. The denticles of the posterior bar and the anterior process are subequal in size and approximately equal to the apical denticle at the juncture of the three limbs. Typically the inner lateral process is the longest and deepest of the three processes. It commonly branches from the posterior bar nearly at right angles but may be in- clined posteriorly or slightly anteriorly and 20 ILLINOIS STATE GEOLOGICAL SURVEY Fig. 14. — Diagrammatic reconstruction of a mature representative of Lambdagnathus Rexroad, n. gen., showing outer lateral (A), aboral (B) and outer posterior (C) views, X35. also is inclined sharply downward. Typi- cally, it is arched, slightly bowed convexly anteriorly, is deepest near its midlength, and has denticles largest near its midsection and decreasing in size in either direction, the larger denticles being considerably larger than the apical denticles. Attach- ment scars may be prominent on the faces of the inner lateral process, less so on the posterior bar and anterior process. Chief variations in the genus are expected to be in the proportions of the lengths of the three processes and their angular relations to each other, plus variations in the dentic- ulation and depths of the processes, partic- ularly the inner lateral one. Relationships of this genus to other gen- era are problematical. The general form is most similar to that of Centrognathodus Branson and Mehl, but it differs particu- larly in the angular relations of the three processes, in the presence of a pronounced triangular subapical pit in Lambdagnathus, and in its triangular apical denticle. Lambdagnathus fragilidens Rexroad, n.sp. Plate 6, figures 10-16 New Genus ? (Part), Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 41, pi. 4, fig. 10 only. Posterior bar delicate, no thicker than the four posteriorly inclined laterally com- pressed denticles it typically bears. Ante- rior process curves outward at juncture of bars, then continues direction of posterior bar. Anterior process thin, of uniform depth, with about twelve denticles which are slightly smaller toward anterior end of process. Inner lateral process viewed orally appears nearly perpendicular to posterior bar, viewed anteriorly is inclined down- ward approximately 45°. Inner lateral process deepest about one-third distance from juncture of processes, with two largest denticles located here, denticles strongly compressed in plane of process, slightly re- curved, and typically number from nine to eleven. Apical denticle larger than den- ticles of posterior bar, triangular in shape with sharp edge in line with each process, slightly recurved. Well defined triangular pit beneath apical denticle with grooves extending from it along the thin aboral margin of each of the processes. Material studied. — 19 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. GLEN DEAN CONODONTS 21 Repository. — Illinois State Geological Survey, 3P31 (holotype), 3P32, 3P33, 3P34, 3P35, 3P36 (paratypes). Genus Ligonodina Bassler, 1925 Type species: Ligonodina pectinata Bassler Ligonodina hamata Rexroad Plate 3, figures 9-14 Ligonodina hamata Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 32, pi. 1, figs. 24, 25. Ligonodina sp., ibid., p. 33, pi. 1, figs. 20, 21. Ligonodina sp., Youngquist and Miller, 1949, Jour. Paleontology, v. 33, no. 6, pi. 101, fig. 11 (not figs. 12, 13). Specimens of Ligonodina from the Glen Dean Formation show that the specimens designated by Rexroad (1957) as Ligono- dina sp., although not typical of L. hamata, must be regarded as belonging to this spe- cies. It seems likely that L. hamata devel- oped from L. obunca by the shift of the inner lateral process to the anterior margin of the terminal fang. This was followed by further development of the proximal por- tion of the inner lateral process. The speci- mens previously referred to as L. sp. by Rexroad represent the extreme develop- ment of this trend but as a variation from the norm. The additional material also shows that four discrete denticles are com- monly present on the inner lateral process. After further study of specimens from both the Pella Beds and the Glen Dean Forma- tion, the figured specimen designated above and referred to L. sp. by Youngquist and Miller (1949) is referred to L. hamata. Material studied. — 1 1 1 specimens from this study, 45 from Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indiana, and Kentucky, and the Pella Beds of Iowa. Repository. — Illinois State Geological Survey, 3P37, 3P38, 3P39, 3P40, 3P41, 3P42, (figured specimens). Ligonodina obunca Rexroad Plate 3, figures 7 and 8 Ligonodina obunca Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 32, pi. 1, figs. 22, 23. Ligonodina sp., Youngquist and Miller, 1949, Jour. Paleontolos^y, v. 23, no. 6, p. 620, pi. 101, figs. 12, 13 (not fig. 11). Study of many complete specimens shows that the inner lateral process of L. obunca typically bears four discrete denticles and that the presence of three or five denticles is less common. The original description of the species stated that the process bore three (or rarely four) denticles. It is partly for this reason that Ligonodina sp. of Youngquist and Miller as represented by two of their figured specimens is now placed with L. obunca. In young specimens of L. obunca the posterior bar is much thinner and the denticles on it more prominent than on adult specimens. Greatest thicken- ing occurs along the anterior portion of the bar. Material studied. — 423 specimens from this study, 65 from Rexroad 1957 study. Distribution. — Renault, Paint Creek, and Glen Dean Formation of Illinois, In- diana, and Kentucky, and the Pella Beds of Iowa. Repository. — Illinois State Geological Survey, 3P43, 3P44 (figured specimens). Ligonodina roundyi Hass Plate 3, figures 1-4 Ligonodina roundyi Hass, 1953, U. S. Geol. Survey Prof. Paper 243-F, p. 82, pi. 15, figs. 5-9; Elias, 1956, Petroleum Geology of southern Okla- homa: Am. Assoc. Petrol. Geol., v. 1, p. 126, pi. V, figs. 10-14. The Glen Dean specimens conform very closely to Hass's type specimens. The den- ticles of the inner lateral process of some Glen Dean specimens are not noticeably compressed. The amount and symmetry of the expansion of the base of the main cusp is variable, as is also true of Hass's type specimens. Material studied. — 32 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky, Barnett Formation of Texas. Repository. — Illinois State Geological Survey, 3P45, 3P46, 3P47, 3P48 (figured specimens). 22 ILLINOIS STATE GEOLOGICAL SURVEY Genus Lonchodina Bassler, 1925 Type species: Lonchodina typicalis Ulrich and Bassler Lonchodina furnishi Rexroad, n.sp. Plate 4, figures 11-13 Arched and slightly bowed unit, limbs thickest at apex and thinning distally. Pos- terior limb the shorter, about three-eighths the length of anterior limb, bowed slightly inward, bearing three or four small, dis- crete denticles strongly compressed later- ally, larger denticles toward posterior tip of limb. Anterior limb the longer, typically inclined downward and only slightly out- ward, bearing seven laterally compressed, recurved, discrete denticles of subequal size. Apical denticle nearly twice as large as denticles of anterior limb, recurved, lat- erally compressed with sharp edges fore and aft, edges in midline of each limb, base of apical denticle expanded into flaring lips about the subapical pit, inner lip flaring in and posteriorly, outer lip flaring out and anteriorly, resulting in a pit which is nearly oval in outline with longest axis oblique to axis of posterior bar. Aborally, faint me- dian groove extends from apical pit to ex- tremities of limbs. The species is named in honor of W. M. Furnish of the State University of Iowa. Material studied. — 13 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P49 (holotype), 3P50, 3P51 (par- atypes). Lonchodina paraclaviger Rexroad, n.sp. Plate 4, figures 7-10 Anterior and posterior limbs thickened, bar-like, each nearly straight but together forming an arched and outwardly bowed unit. Considering the slight curvature of the denticles of some specimens, the shorter limb is designated the posterior limb in the orientation of this species. Posterior limb averages one-half length of anterior limb, is slightly bowed convexly inward, typically bears four small laterally compressed, dis- crete denticles. Anterior limb inclines out- ward up to 35° from line of posterior bar, is very slightly bowed outward, and bears six, seven, or eight denticles which are lat- erally compressed, sharp-edged fore and aft, and in some specimens fused about a third of the distance up from the base. In a num- ber of specimens the denticles toward the distal end of the bar are increasingly large. Apical denticle usually, although not al- ways, the largest denticle, sharp-edged fore and aft, inner face the more convex, nearly straight, may incline slightly posteriorly and inward. Aboral margin of each limb rounded with a faint median groove extend- ing the length of each limb from a sub- triangular apical pit which has a straight outer margin and a sharply flaring inner lip. The thickening of the limbs of this spe- cies results in a form approaching the genus Geniculatus Hass. However, the accretion of lamellae in building a heavier limbed form has not progressed to the point of building the geniculate unit characteristic of Geniculatus. Material studied. — 19 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P52 (holotype), 3P53, 3P54, 3P55 (para types). Lonchodina cf. L. paraclarki Hass Plate 4, figures 4 and 5 Lonchodina paraclarki Hass, 1953, U. S. Geol. Sur- vey Prof. Paper 243-F, p. 83, pi. 16, figs. 15, 16. The specimens from the Glen Dean For- mation are very similar to the holotype of L. paraclarki Hass. The apical denticles of some Glen Dean specimens are slightly broader and shorter than those of the holo- type, but this may well come within the range of individual variation. One of the Glen Dean specimens has a complete pos- terior bar which bears six widely spaced denticles. This is contrary to the descrip- tion of L. paraclarki, but in my opinion, based on examination of the type speci- GLEN DEAN CONODONTS 23 mens of L. paradarki, the posterior bars of both the holotype and figured paratype are broken. In the Glen Dean specimens this bar is twisted so that the denticles on it, although normal to the bar, curve toward the outer side of the fossil. Apparently there is a typographical error in labeling of Mass's figures 15 and 16 of plate 16 as both views are labeled as showing the outer side. Actually the greater expansion of the base of the apical denticle is on the inner side. Material studied. — 8 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky, the Bar- nett Formation of Texas. Repository. — Illinois State Geological Survey, 3P56, 3P57 (figured specimens). Crenus Neoprioniodus Rhodes and Miiller, 1956 Type species: Prioniodus conjunctus Gunnell Neoprioniodus camurus Rexroad Plate 5, figures 5 and 6 Neoprioniodus cainurus Rexroad^ 1957, Illinois Geol. Survey Rept. Inv. 199, p. 33, pi. 2, figs. 18-20. Some of the Glen Dean specimens of N. camurus have as many as fifteen denticles on the posterior bar. Complete specimens show that the terminal fang is rather short, tapering uniformly to a point. None of the Glen Dean specimens have the relatively thick posterior bar which was noted in four specimens from the Renault and Paint Creek Formations. Material studied. — 44 specimens from this study, 20 from the Rexroad 1957 study. Distribution. — Renault, Golconda, Glen Dean, Menard, and Kinkaid Formations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P58, 3P59 (figured specimens). Neoprioniodus loxus Rexroad Plate 5, figures 7-9 Neoprioniodus loxus Rexroad^ 1957, Illinois Geol. Survey Rept. Inv. 199, p. 34, pi. 2, figs. 8, 9, 14. Neoprioniodus tenuis Rexroad, 1957, ibid., p. 35, pi. 2, figs. 13, 16. A number of specimens intermediate be- tween N. loxus and N. tenuis were found in this study. The two extremes are read- ily distinguishable on the basis of differ- ences in cross-section shape of the posterior bar. N. tenuis has a proportionately deeper and thinner bar. However, the presence of intermediate specimens gives a gradational series between the two extremes, and it seems best to place the two in synonomy. Material studied. — 49 specimens from this study, 35 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, and Menard For- mations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey 3P60, 3P61, 3P62 (figured speci- mens). Neoprioniodus scitulus (Branson and Mehl) Plate 5, figures 10-14 Prioniodus scitulus Branson and Mehl^ 1940, Deni- son Univ. Bull., Jour. Sci. Labs., v. XXXV, p. 173, pi. V, figs. 5, 6; Cooper, 1947, Jour. Paleon- tology, V. 21, no. 2, p. 92, pi. 20, figs. 1-3; Elias, 1956, Petroleum Geology of southern Okla- homa: Am. Assoc. Petrol. Geol., v. 1, p. 109, pi. II, figs. 9, 10. Neoprioniodus scitulus (Branson and Mehl), Rex- road, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 35, pi. 2, figs. 22, 26. Neoprioniodus striatus Rexroad, 1957, ibid., p. 35, pi. 2, figs. 11, 12. This is an abundant and somewhat vari- able species in the Glen Dean Formation. The anterior margin of the fang, viewed laterally, may be straight or convex in the adult and is usually more convex in the young. The length of the aboral projection of the fang varies as does the outline of the aboral margin. The outline may be slightly convex posteriorly or straight, more convex in the young specimens which may have well developed, slightly flaring lateral lips, which disappear in the adult form. The base of the aboral projection is excavated in the young but fills in during growth leav- ing a tiny pit with a longitudinal median groove extending anteriorly and posterior- ly from it. With growth lateral attachment scars may become prominent on the aboral projection of the fang. Other variations 24 ILLINOIS STATE GEOLOGICAL SURVEY are shown by slight differences in the height and thickness of the posterior bar. The variations in shape and length of the aboral projection of the fang, as well as the convexity of the anterior margin of the fang, are reflected in the young. About two dozen young specimens were sufficiently distinctive that their relationship to the adult was not recognized in an earlier study (Rexroad, 1957). They were named as a new species, N. striatus. The additional specimens recovered from the Glen Dean Formation show the variations among the young and the gradation from the young to the mature stage, as well as adult speci- mens which still retain to some degree the aberrant youthful characteristics upon w^hich A^. striatus was based. Therefore^ A^. striatus is placed in synonomy with A^. scitu- lus. Material studied. — 548 specimens from this study, 100 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indiana, and Kentucky, and the Delaware Creek Member of the Caney Shale of Oklahoma. Repository. — Illinois State Geological Survey, 3P63, 3P64, 3P65, 3P66, 3P67 (fig- ured specimens). Neoprioniodus varians (Branson and Mehl) Plate 5, figures 3 and 4 Prioniodus varians Branson and Mehl, 1940, Deni- son Univ. Bull., Jour. Sci. Labs., v. XXXV, p. 174, pi. V, figs. 7, 8; ? Bischoff, 1957, p. 49, pi. 5, fig. .35; Flugel and Ziegler, 1957, p. 50, Neoprioniodus varians (Branson and Mehl), Rex- road, Illinois Geol. Survey Rept. Inv. 199, p. 35, pi. 2, fig. 10. The Chester specimens, although varia- ble, conform well to the Caney Shale forms. The species is similar to N. loxus but differs chiefly in the angle between the fang and posterior bar from lateral view. In N. varians it is about 100°, in N. loxus about 135°. Also, the inner lip on the aboral pro- jection of N. loxus flares more markedly. Material studied. — 121 specimens from this study, 10 from the Rexroad 1957 study. Distribution. — Paint Creek, Glen Dean, and Clore Formations of Illinois, Indiana, and Kentucky, also the Caney Shale of Oklahoma. Repository. — Illinois State Geological Survey, 3P68, 3P69 (figured specimens). Genus Ozarkodina Branson and Mehl, 1933 Type species: Ozarkodina typica Branson and Mehl Ozarkodina compressa Rexroad Plate 6, figures 1 and 2 Ozarkodina compressa Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 36, pi. 2, figs. 1, 2. The majority of specimens of O. com- pressa found in the Glen Dean Formation correspond closely to the holotype and par- atype of the species. A few specimens vary in being markedly more elongate than the average, and some specimens are slightly less arched than the remainder. Young specimens have fewer denticles, a propor- tionately larger subapical pit, and lack germ denticles. Material studied. — 243 specimens from this study, 25 from the Rexroad 1957 study. Distribution. — Golconda, Glen Dean, Menard, and Kinkaid Formations of Illi- nois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P70, 3P71 (figured specimens). Ozarkodina curvata Rexroad, n.sp. Plate 4, figures 1-3 Strongly arched and bowed, thin, blade- like unit with posterior limb less arched; the anterior limb typically has four or five laterally compressed denticles fused about two-thirds the distance to the apices; den- ticles decrease slightly in size anteriorly; denticles of the posterior limb number about nine to eleven and are laterally com- pressed, fused about one-half to two-thirds distance to the apices, and of somewhat varying sizes. Typically the denticles of the posterior limb are smaller than denticles of the anterior limb and suppressed germ den- ticles are commonly present. The apical denticle is twice the width of adjacent an- terior denticles, is longer, tapers to a point, and is laterally compressed with GLEN DEAN CONODONTS 25 sharp edges fore and aft, inclined slightly posteriorly. The navel is very small, mod- erately deep, asymmetric in outline, with the inner margin nearly straight, the outer margin with slightly flaring lip, the pos- terior end pointed and continued as a faint groove along the aboral margin of the pos- terior bar. The anterior end of the navel is rounded. Chief variation in this species is in the size of the denticle on the posterior limb. Limbs of some specimens bear denticles of a single size, but on other specimens den- ticles are of varying sizes. Because the posterior limb is longer than the anterior limb, is bowed but otherwise nearly straight, and because the denticles on it may vary in size, this species bears a resemblance to the group of hindeodellids in which the anterior process is sharply downturned in a "pick-like" manner. Material studied. — 38 specimens. Distribution. — Renault and Glen Dean Formations of Illinois, Indiana, and Ken- tucky. Repository. — lUinois State Geological Survey, 3P72 (holotype), 3P73, 3P74 (para- types). Genus Spathognathodus Branson and Mehl, 1941 (Spathodus Branson and Mehl, 1933) Type species: Spathodus primus Branson and Mehl Spathognathodus campbelli Rexroad Plate 6, figure 9 Spathognathodus campbelli Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 37, pi. 3, figs. 13-15. The representatives of this species found in the Glen Dean closely resemble the pre- viously described specimens. Material studied. — 12 specimens from this study, 65 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, and Kin- kaid Formations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P79 (figured specimen). Spathognathodus cristula Youngquist and Miller Plate 6, figures 3 and 4 Spathognathodus cristula Youngquist and Miller, 1949, Jour. Paleontology, v. 23, no. 6, p. 621, pi. 101, figs. 1-3; Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 38, pi. 3, figs. 16, 17. This is one of the least variable and most abundant Glen Dean species. All speci- mens are very similar to the holotype and para types. Material studied. — 367 specimens from this study, 50 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard and Clore Formations of Illinois, Indiana, and Ken- tucky, and the Pella Beds of Iowa. Repository. — Illinois State Geological Survey, 3P80, 3P81 (figured specimens). Spathognathodus spiculus Youngquist and Miller Plate 6, figures 5-7 Spathognathodus spiculus Youngquist and Miller, 1949, Jour. Paleontology, v. 23, no. 6, p. 622, pi. 101, fig. 4; Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 38, pi. 3, figs. 18-21. Spathognathodus bidens Youngquist and Miller, Jour. Paleontology, v. 23, no. 6, p. 621, pi. 101, fig. 5. The Chester representatives of this spe- cies show a great amount of variation, par- ticularly in the number and shape of the major anterior denticles. The large num- ber of specimens available show a unity in this variable group and include specimens nearly identical to the holotype of S. bidens as well as of S. spiculus indicating that the two represent a single species. Because the great majority of specimens conform more closely to S. spiculus, that name is retained in preference to S. bidens. Material studied. — 175 specimens from this study, 90 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore, and Kinkaid Formations of Illinois, Indiana, and Kentucky, and the Pella Beds of Iowa. Repository. — Illinois State Geological Survey, 3P82, 3P83, 3P84 (figured speci- mens). 26 ILLINOIS STATE GEOLOGICAL SURVEY SpATHOGNATHODUS Ct. S. COMMUTATUS Branson and Mehl Plate 6, figure 8 Spathognathodus commutatus Branson and Mehl, 1941, Jour. Paleontology, v. 15, no. 2, p. 98, pi. 19, figs. 1-4. Spathognathodus cf. S. commutatus Branson and Mehl, Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 38, pi. 3, figs. 23, 24. Chester specimens have a thinner lipped, proportionately longer navel, and fewer denticles than do Branson and Mehl's syn- types from the Pitkin limestone, and it is still felt that the differences of the Chester specimens do not justify the erection of a new species. Material studied. — 8 specimens from this study, 10 from the Rexroad 1957 study. Distribution. — Renault, Paint Creek, and Glen Dean Formations of Illinois, In- diana, and Kentucky. Repository. — Illinois State Geological Survey, 3P85 (figured specimen). Genus Roundya Hass, 1953 Type species: Roundya barnettana Hass Roundya costata Rexroad, n.sp. Plate 2, figures 5-8 Cusp large, recurved, sharpest curvature about one-third distance above base, sharp lateral edges, sharp edges expanding toward base into distinct ridges continuous with lateral bars, distal anterior and posterior faces of cusp convex, basally anterior face becomes nearly flat and posterior face de- velops sharp edge passing into slight ridge which merges into oral surface of posterior bar. Posterior bar widest anteriorly where it merges with expanded base of cusp, bar tapers sharply posteriorly and continues as very thin bar which is rarely preserved, bar bears a few discrete denticles. Lateral limbs thick, none complete, bear closely spaced, slightly compressed, discrete denticles; limbs inclined slightly backward and down- ward about 45° to 55°. Aboral margin marked by deep pit beneath cusp, triangu- lar in outline with apex of triangle poste- rior, pit continued as faint median grooves along aboral margins of posterior bar and lateral limbs. Material studied. — 13 specimens. Distribution. — Glen Dean Formation of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P75 (holotype), 3P76, 3P77, 3P78 (para types). Genus Trichonodella Branson and Mehl, 1948 ( Trichognathus Branson and Mehl, 1933) Type species: Trichognathus prima Branson and Mehl Trichonodella imperfecta Rexroad Plate 4, figure 6 Trichonodella imperfecta Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 41, pi. 4, figs. 4, 5. The few specimens recovered in this study are nearly identical with the previ- ously described material from the Chester Series of southwestern Illinois. Material studied. — 6 from this study, 10 from the Rexroad 1957 study. Distribution. — Renault, Glen Dean, and Kinkaid Formations of Illinois, Indiana, and Kentucky. Repository. — Illinois State Geological Survey, 3P86 (figured specimen). Genus Indeterminate Plate 5, figures 1 and 2 Lonchodina sp. Branson and Mehl, 1940, Denison Univ. Bull., Jour. Sci. Labs. v. XXXV, p. 171. pi. V, figs. 10, 12. Lonchodina ? spp., Youngquist and Miller, 1949, Jour. Paleontology, v. 23, no. 6, p. 620, pi. 101, figs. 7, 8. Metalonchodina sp. B, Elias, 1956, Petroleum Ge- ology of southern Oklahoma: Am. Assoc. Petrol. Geol., V. 1, p. 124, pi. V, fig. 2. Metalonchodina ? sp., Elias, 1956, ibid., p. 124, pi. V, fig. 3. Genus Indeterminate, Rexroad, 1957, Illinois Geol. Survey Rept. Inv. 199, p. 42, pi. 4, figs. 19-22. Several hundred fragments fail to give an adequate picture of this group of conodonts upon which to base a generic determination because in no single specimen are both limbs completely preserved. Because one limb is fragile, it commonly is represented only by a fracture or by a very short stub. When a stub is present, a pit can be seen on its aboral margin near the juncture of the two main portions, but in a number of GLEN DEAN CONODONTS 27 specimens there is no main denticle or cusp above the pit, only small denticles. I would interpret the form as consisting of a bar with or without a small main cusp, a deep pit near the anterior end of bar, and, rising from the anterior end of the bar, an antero-lateral process directed downward and slightly backward, bowed convexly posteriorly, and bearing several stout dis- crete denticles, the antero-lateral process considerably larger than main bar. The specimens seem more closely related to Ligonodina than to any other described genus. Material studied. — 140 specimens. Distribution. — Renault, Paint Creek, Golconda, Glen Dean, Menard, Clore and Kinkaid Formations of Illinois, Indiana, and Kentucky, the Pella Beds of Iowa, and the Delaware Creek Member of the Caney Shale of Oklahoma. Repository. — Illinois State Geological Survey, 3P87, 3P88 (figured specimens). REFERENCES BiscHOFF^ GuNTHER, 1957, Die Conodonten-Strati- graphie des rheno-herzynischen Unterkarbons: Hess. Landesamt. Bodenf., Abhl., Hf. 19, p. 1-64, pi. 1-6. Branson, E. B., and Mehl, M. G., 1940, Caney Con- odonts of Upper Mississippian age: Denison Univ. Bull., Jour. Sci. Labs., v. XXXV, p. 167- 178, pi. V. Branson, E. B., and Mehl, M. G., 1941, New and little known Carboniferous conodont genera: Jour. Paleontology, v. 15, no. 2, p. 97-106, pi. 19. BuRMEiSTER, H. C. C, 1847, Handbuch der Ento- mologie, v. 5, p. 364. Cooper, Chalmer L., 1947, Upper Kinkaid (Missis- sippian) microfauna from Johnson County, Illi- nois: Jour. Paleontology, v. 21, no. 2, p. 81-94, pis. 19-2.?; reprinted as Illinois Geol. Survey Rept. Inv. 122. Elias, Maxim K., 1956, Upper Mississippian and Lower Pennsylvanian formations of south-cen- tral Oklahoma: Petroleum geology of southern Oklahoma: Am. Assoc. Petrol. Geol., v. 1, p. 56-134, pi. I- VI. Flugel, von, Helmut, and Ziegler, Willi, 1957, Die Gliederung des Oberdevons und Unter- karbons am Steinberg westlich von Graz mit conodonten: Naturwissenschaft. vereines f. Steiermark, Mitteil. Bd. 87, p. 25-60, pi. 1-5. Hass, Wilbert H., 1950, Age of lower part of Stan- ley Shale: Am. Assoc. Petrol. Geol. Bull., v. 34, no. 7, p. 1578-1584. Hass, Wilbert H., 1953, Conodonts of the Barnett Formation of Texas: U. S. Geol. Survey Prof. Paper 243-F, p. 69-94; pi. 14-16. Hass, Wilbert H., 1954, Age of some black shales in cores from northeast Mississippi: Mississippi Geol. Soc. Guide Book, 11th Field Trip, p. 32-33. Rexroad, Carl B., 1957, Conodonts from the Ches- ter Series in the type area of southwestern lUi nois: Illinois Geol. Survey Rept. Inv. 199, p. 1-43, pi. 1-4. YouNGQUiST, Walter, and Miller, A. K., 1949, Con- odonts from the late Mississippian Pella Beds of south central Iowa: Jour. Paleontology, v. 23, no. 6, p. 617-622, pi. 101. Illinois State Geological Survey Report of Investigations 209 27 p., 6 pis., 14 figs., 1 table, June 1958.