EVOLUTION OF THE HORSE 15 
and these are just beginning to show signs of fusing into cross- 
crests. The premolar teeth have only one main cusp, except the 
third and fourth premolars (next the molars) in each jaw, which 
have two and three, respectively. The only specimens which 
have been found were in the London Clay or Lower Eocene of 
England and are preserved in the British Museum. 
The Eohtppus is much better known. It comes from the Lower 
Eocene of Wyoming and New Mexico, and is very like the Hy- 
FIG. 1.—UPPER AND LOWER TEETH OF “ EOHIPPUS,’”? FROM 
THE LOWER EOCENE OF WYOMING. NATURAL SIZE 
racothertum except that the molar teeth have the cusps more 
clearly fusing into cross-crests, and the last premolar is begin- 
ning to look like one of the true molars. The forefoot of this 
animal has four complete toes and the splint of a fifth. The 
hindfoot has three complete toes and the splint of another. A 
specimen of the hindfoot is shown in the series in the A-case and 
many incomplete specimens, skulls, jaws etc., of several species 
in the counter-case. 
3 and 4. Protorohippus and Orohippus. MippLe Eocene. 
In these animals the splint of the first digit in the forefoot and 
the splint of the fifth digit of the hindfoot have disappeared, but 
there are still four complete toes in the fore- and three in the hind- 
foot. The crests on the molars are a little clearer and the last 
premolar has become almost like the molars, while the next to 
the last premolar is beginning to become so. A skeleton of 
Protorohippus is mounted in the wall-case. It shows an animal 
of the size of a small dog, and proportioned much like the breed 
known as the whippet, of which a skeleton has been placed near by 
for comparison with the Protorohippus skeleton. The Protoro- 
hippus was found by Dr. J. L. Wortman in 1880 in the Wind 
