264 APPENDIX. 



Prof. Cope in the Wasatch beds of New Mexico, and described 

 by him in his report to Captain Wheeler, already cited. It 

 was formerly arranged in the Ckalicot/ieriidce, near Chalicothe- 

 rium, with which it agrees in all essential dental characters. 

 The recent discovery of the bones of the feet shows that they 

 display the characteristic peculiarities of the Condylarthra, to 

 which group it must be referred. Its digital formula is 

 unknown, hence we must rely on the specialized crescentoid 

 pattern of the molars for the family definition. It is proper to 

 remark here that reduction in digits in the Perissodactyla is 

 usually accompanied by specialization of the molar teeth. In 

 this case, therefore, I would venture the prediction that its 

 digital formula will be found to be 4 3, with the outer toes 

 somewhat reduced. The value of the digital formula as a 

 character in the definition of the families of the Perissodactyla 

 is of high standard. This may likewise be said of the rela- 

 tion of the molar and premolar teeth, but in a less degree. 

 The tubercular or crescentoid structure of the molars, however, 

 is capable of such intergradation, which increase of our knowl- 

 edge demonstrates, that it must be accepted as provisional 

 only, and not entitled to rank equal in value to either of the 

 other two characters in defining the family. 



The genealogy of the horse as now indicated is as follows : 



Equus, Equus, 



Protohippus, Hippotherium, 



Anchippus, Paloplotherium, 



Anchitherium, 

 PERISSODACTYLA - < , r , . 



Mesohippus, 



Lambdotherium, 



Hyracotherium, 



Systemodon. 



AMBLYPODA, Hyodonta (Cope). 



CONDYLARTHRA - ! Meniacotherium, 



( Phenacodus. 



