SOME EARLY MAMMALS 245 
=< 
1. Hyracothervum 
= Protorohippus. 
2. Orohippus. 
3. Mesoluppus 
allied to the 
Anchithervum. 
4, Merychippus 
(Protohippus). 
5. Pliohippus. 
YS a on 
te ) aia Rte, 
\ ANS AN 
-\ ' \ \\ Ye 
WW WTK\' 
Ny WAN \. 
6. Equus caballus. 
\ 
AN, 
i 
‘\ 
E> 
> 
Fic. 90.—The Evolution of the horse. 1-5, ancestors of the horse restored in 
outline from fossil remains from the Lower Eocene to recent times. 
(H. 8S. Lull, American Jour. Science, vol. xxiii.) 
