SOME EARLY MAMMALS 
243 
was a graceful little creature about fourteen inches (four and 
Fig. 89, — Skulls and bones of fossil horses showing evolution of the horse, 
from casts in the Natural History Museum, London. 
1. Protorohippus (= Hyracotherium.) 2. Mesohippus. 3. Protohippus, 
4. Hipparion. 5. Equus caballus. 
a half hands) high at the withers. The next stage is seen in 
