388 



DARWINISM 



CHAP. 



Hind- Fore- T arf 

 foot. arm. ^ 



RECENT. 

 Equus. 



PLIOCENE 

 Pliohippus. 



Protohippus 

 (Hipparion). 



MIOCENE. 



Miohippus 

 (Anchitherium). 



Mesohippus. 



EOCENE. 

 Orohippus. 



Fig. 33.— Geological development of the horse tribe (Eohippus since discovered). 



