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 



