EVOLUTION OF THE HORSE 19 
while in the Upper Oligocene occurs Mesohtppus intermedius as 
large asa sheep. Of both these animals all parts of the skeleton 
are known, and a good series of skulls, feet, jaws, palates etc. is 
FIG. 2.—UPPER AND LOWER TEETH OF “ MESOHIPPUS BAIRDI,”” 
FROM THE MIDDLE OLIGOCENE OF SOUTH DAKOTA. NATURAL SIZE 
exhibited in the counter-case, besides the specimens shown in the 
_ series of feet and in the series of skulls. 
8. Anchitherium. Lower Miocene. This stage has been 
found both in Europe and in America. It is much like its prede- 
cessor, but is larger and has the crests of the teeth somewhat 
higher and more complete. It probably is not in the direct line of 
descent of the horses, but is on a side branch. A palate, jaws, 
teeth and foot-bones are exhibited here. 
9. Parahippus and Hypohippus. Mippie Miocene. In Par- 
ahippus the tooth-crests are much higher, and the transverse 
ridges on the upper molars are beginning to change shape so as to 
become a second pair of crescents inside the outer pair. Hypo- 
hippus is off the direct line of descent; its teeth are like those of 
Anchitherium, by which name it has been generally called, but 
the animal was much larger, equalling a Shetland pony in size. A 
complete skeleton of the Hypohippus is shown in wall-case 15, 
and illustrates very well the general characters of the Three-Toed 
Horses, although it is not in the direct line. This specimen was 
found near Pawnee Buttes, Colorado, in 1901 by Barnum Brown, 
of the Whitney expedition. Other incomplete specimens of 
Hypohippus, Parahtppus and Merychippus are shown in the 
counter-case, and casts of the feet and skull in the evolution se- 
ries in A-Case 49. It may be observed that in the forefoot of 
