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 



