SOME EARLY MAMMALS 243 
was a graceful little creature about fourteen inches (four and 
Fia. 89,—Skulls and bones of fossil horses showing evolution of the horse, 
from casts in the Natural History Museum, London, 
1. Protorohippus (= Hyracotheriwm.) 2. Mesohippus. 38. Protohippus. 
4, Hipparion. 5, Hquus caballus, 
a half hands) high at the withers. The next stage is seen in 
