270 PALEONTOLOGY OF ILLINOIS. 



Cladodus belllfer, St. J. and W. 



PI. 4, Fig. 10. 



The teeth attain large size. Outline of base subelliptical, extremities 

 rounded, posterior margin broadly rounded, anterior border of mode- 

 rate depth, slightly iubevele'd, gently concave in the middle, rather 

 abruptly rounded laterally, median ridge occupying half or more of the 

 lateral diameter, moderately prominent as are also the anterior basal 

 angles, inferior surface gently concave, with broad beveled belts along 

 the posterior margin, postero-superior surface occupied by a prominent, 

 narrow ridge whicli extends over two-thirds the lateral diameter, 

 abruptly defined behind and parallel with the posterior border. Crown 

 slightly constricted basally in frout, median cone strong, gradually 

 tapering, moderately recurved or nearly vertical to the horizontal plane 

 of base, sublenticular in transverse section with sharp lateral edges, 

 much compressed below in front, gently convex above, strongly so 

 behind, apex sharp or obtusely truncated from wear; lateral denticles 

 two on either extremity, moderately strong, exterior pair slightly diver- 

 gent, recurved iu the same plane as the median cone aud similar in 

 shape, inner pair prominently produced in front and generally much 

 abraded; coronal surfaces without trace of ornamentation, presenting 

 a smooth appearance, as from wear. A remarkably fine large specimen 

 in the collection of Mr. Springer measures in greatest diameter of 

 base 1.4 inches, autero-posterior diameter .62, greatest hight of tooth 

 1.20 inches. 



. The collection of Mr. Speinger contains a few examples of the form 

 above described, which show considerable variation in size, and always 

 the appearance of wear, but well characterized by the advanced position 

 of the inner pair of lateral denticles. In the latter respect it resembles 

 ft oecidentalis, Leidy, of the Coal Measures, although otherwise not inti- 

 mately related to that form, as indicated by the continuity of the ante- 

 rior basal ridge and the prominence in the postero-superior surface. 

 The worn condition of the specimens renders it doubtful whether the 

 coronal surfaces were plain or their costse obliterated by abrasion. 



Position and locality : Upper Burlington fish-bed, Louisa county, and 

 Burlington, Iowa. 



Cladodus pr^nuntius, St. J. and W. 



PI. 4, Fig. 17. 



We have provisionally recognized, in a unique example in the collec- 

 tion of Mr. Springer, the representation of a distinct form. The tooth 

 is of medium size, strong, symmetrical proportions. The base is very 



