162 B. S. Lull— The Evolution of the Horse Family. 



RECENT 



Fore Foot Hind Foot Fore-ann Leg Upper Molar Lower Molar 



o 



PLIOCENE 



PLIOHIPPfS 



PEOTOHIPPI'S 



(Hipparion) 



MIOCENE 



MIOHIPPUS 



{Ancliitherium) 



MESOHIPPUS 



EOCENE 



OEOHIPPVS 



Fig. 2. Genealogy of the Horse. (After Marsh.) 



