JR. S. Lull — The Evolution of the Horse Family. 167 



6 



a. 



d 



Fig. 6. Prehistoric horses compared with the modern horse in size and 

 contour ; a, Protorohippus ("Wind Eiver Eocene) ; b, Orohippus (Bridger 

 Eocene) ; e, Mesohippus (Oligocene) ; d, Merychippus (Miocene) ; e, Pliohippus 

 (Pliocene) ;/, Equus (Eecent). (Original.) 



