1896.] 



173 



[Farr. 



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

 proximally. 



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

 following diagram : 



Protoceras Beds. 



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



Orcodon 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 follovrs : 



Pliocene to Recent 



Loup Fork 



Deep River 



Equus 



John Day 



White River 



Uinta 



Bridffer 



Wasatch 



Puerco Condylarthra 



J: Represents the line of descent. 



Hippidium 



Protohippus Hipparion 



Desmatippus Anchitherium 



Mesohippus 



Mesohippus 



Epihippus 



Pachynolophus 



Hyracotherium Palseotherium 



Protogonia 

 Protogouodon 



