H. F. shorn — Mammalia in North America. 



451 



therium, because the "crescenfcic spurs" of the horse and the 

 " crochet " and " antecrochet " of the rhinoceros spring alike 

 from the primitive "intermediate tubercles." 



In view of these discoveries of the uniformity of mamma- 

 lian molar type, a uniform terminology has become as neces- 

 sary for the dental cusps as for the carpal and tarsal elements 

 of the feet. Professor Gaudry's once admirable system, elabo- 

 rated in his " Enehainements" was based upon the supposed 



Euprotogonia. 

 4th Pm, 1st M. 



Hyracotherium. 

 4th Pm. 1st M. 



Anchitherium, 1st M. Coryphodon, 1st M. 



Homologies in the Horse and Coryphodon Molars and Premolars. 



division of the ungulate molar into a "first lobe" and 

 " second lobe," and is still followed in France. Yet it has two 

 drawbacks: it precludes the comparison of the ungulate with 

 the unguiculate molar, for neither lobe includes the complete 

 triangle ; still more inconvenient is the fact that we cannot 

 compare the higher ungulates with the older Coryphodons and 

 Periptychidse in which the molars were developed upon the 



