1898.] Osborn^ Evolution of the Auiblypoda. Part I. 



193 



Thus the crests of the upper and lower molars slowly become 

 transverse, and simultaneously also preserve their mutual inter- 

 locking shear ; the stages, i, 2 and 3, in each being probably 

 correlated. 



It is, however, extremely difficult to determine the species by 

 these principles alone, because the hypolophid, or posteiior crest, 

 of the third lower molar seems to be highly variable, not in its 

 obliquity of angle, but in the greater or less development of the 

 eutoconid 2, as frequently seen upon opposite sides of the same 

 jaws {e. g., Nos. 286S and 4321). 



Cutting Teeth.— The eaniiies aid us : the primitive form is 

 round (])ersisting in C. wortniani) as in Pantolatnbda ; the inter- 

 mediate form is tri- 

 angular and antero- 

 posteriorly compressed 

 {C. testis, C. ventanits) ; 

 the final form is flat- 

 tened and laterally 

 compressed {C. amia- 

 tus), paralleling the 

 Uintatherium type, be- 

 cause the long axis of 

 the blade is longitudi- 

 nal. 



Skull. — When fully 

 known, the to]) of the 

 skull will prove highly 

 distinctive. At present 

 we know only the com- 

 paratively primitive 

 crested type (Fig. 18 />'), 

 and the flattened type 

 (Fig. t8 6'), which ap- 

 proaches Uintatherium. 

 [May, /<?9cP.J 



Fig. 17. Upper and lower canines, lateral views and 

 sections. A^ Coryphodon testis, i . male npper and lower 

 canines, No. 274. 9 , female lower canine. />', C. a>tn.v, 

 male lower canine, No. 4328. C, C. Teniaiius, male 

 upper canine, No. 2970. D, C. armaiiis, upper canine 

 and section, No. 4315. This very small canine is upon 

 double the scale of the other teeth. 



13 



