19^ Bulletin American M useujH of Natural History. [Vol. X, 



r C. ductus. 



C. anax. 



m.3 en' 



2. C. radians pre- 

 sents an intermediate 

 stage, ectoloph (with 

 crescents and meso- 

 style disappearing) 

 oblique to protoloph 

 (Fig. is). 



3. C. anuatus pre- 

 sents a final stage, 

 oval crown, ectoloph 

 (a slightly concave 

 cvt^i) parallel to pro- 

 toloph (Fig. 15). 



The second upper 

 molar slowly goes 

 through the same 

 phases as the thirtl, 

 and both approach 

 the Uiiitatherium 

 pattern. 



In the third hnvcr 

 molar various species 

 of Coryphodon ex- 

 hibit (Fig. 16) : 



I. Primitive stage, 

 a trilobed heel (hypo- 

 conid, entoconid, en- 

 toconid 2) ; crests 

 oblique, heel with 

 three main cusps, 

 C. eoccenus. 



2. Intermediate 

 stage, a heel with two 

 main cusps (hyi)O- 

 conid, entoconid), 

 third cusp (entoconid 2) degenerate ; crests less oblique, C. testis. 

 3. Final stage, a bilobed heel (hypoconid, entoconid), ento- 

 conid 2 absent, crests transverse, C. sin/us. A tooth exactly of the 

 Tapir or i>ophiodon type. 



-'"•2 m.3 „„ 



C. ventainis. 



m:3 

 C. ciirvicristis. 



"'■2. m.3 



C.S 1)1 Ills. 



C .ai'Diatus. 



Fig. 16. Typical lower molars. C. eoctenus, cast of Owen's 

 type. C. testis. C. cinctus. variety, with triangular heel. No. 

 4329. C. lobatus^ typical lower molar, No. 4305. C. ventanus^ 

 type, No. 2970. C. ciirvicristis, type, No. 4326. C. siiiiiis. 

 No. 2563. C. artiiaius, type, No. 4316. All in the Am. Mus. 

 Coll. 



