3 6 
W. J. MARTIN. 
/ 
of the zygomatic. The uumber of vertebrae was as follows: 
Cervical, 7; dorsal, 14 to 15; lumbar, 6 or 7; sacrum, 3 or 5; 
caudal bones present are 11, but many more are wanting, as 
the tail was very long. Cope, in referring to a restoration of 
this animal, says: “The foregoing measurements show that 
Phenacodus Primaraeur was in-size between that of a tapir and 
a sheep. Its body was rather longer than these animals, and 
its legs shorter and more robust, This animal was omnivorous 
in its diet.” Next in upward succession comes an animal known 
as Hyracotherium. Here we find a distinct advance over 
Phenacodum. Hyracotherium, having but four toes on each 
front limb, and but three on the hind ones, I may say in passing 
that the change from Phenacodus to Hyracotherium was not 
sudden, but, on the contrary, was very gradual, as we can trace 
the ruins of several families between Phenacodus and Hyraco¬ 
therium. Among these may be mentioned Memeotherium and 
Systemodon. These genera were all five-toed, and the species 
belonging to them serve as a bridge to connect the families of 
Phenacodus and Hyracotherium. The dental formula in Hyra¬ 
cotherium was the same as in Phenacodus, but the triturating 
surface showed a more complex structure. The size of this 
animal ranged from that of a fox to a sheep. The remains of 
this animal has been found very extensively in the Wasatch 
beds of Eocene age in this country, and also in the London 
Clyde of the same period in England. The next animal con¬ 
nected by national affinities with Hyracotherium, but of a 
higher order, is Anchitherium. The remains of this gender has 
been found in abundance in the miocene foomation of the Bad 
Lands of the White River, Dakota. In general outline the 
skull of this animal bears a striking similarity to that of the 
horse. The number of teeth possessed by this animal was 44 
in number, and are identical in form with those of the same 
family found in France. Although the teeth of this animal 
number 44, we can see a great reduction in size of the first 
premolars in each jaw, which goes to show that even at that 
early day the process of eliminating the supernumerary teeth 
