1896.] 



173 



[Farr. 



bones and closely applied to M. iii, M. iv is still larger than M. ii 

 proximally. 



The inter-relationships of these three species may be expressed by the 

 following diagram : 



Protoceras Beds. 



M. bairdi. M. intermedins. M. copei. 



Oreodon Beds. / M. bairdi. 



M. copei. 



Titanotherium Beds. / M. bairdi. 



The phylogeny of the horse series as it is now generally understood 

 may be given as follows : 



Pliocene to Recent 



Loup Fork 



Deep River 



Equus 



Hippidium 



Protohippus Hipparion 



Desmatippus Anchitherium 



John Day 



White River 



Uinta 



Bridger 



Wasatch 



Mesohippus 



Mesoiiippus 



Epihippus 



Pachynolophus 



Hvracotherium Palseotherium 



Puerco Condylarthra 



l Represents the line of descent. 



Protogonia 

 Protogonodon 



