504 



CENOZOIC TIME. 





On Plate VI., Fig. 1 gives the form of the skull, and of the very 

 small brain (b) ; 2, a larger figure of the brain, shows the small size of 

 the anterior or cerebral part as compared with the posterior or cere- 

 bellar part ; and 3 and 4 represent a fore-foot and hind-foot. 



Along with the Corjphodonts existed other kinds (Helaletes Marsh, 

 Hyrachyus Leidy), that were more Tapir-like, the fore-feet having 

 four toes, and the hind three, — the first or inner toe being wanting in 

 the former, and the first and fifth in the latter ; but the nose and the 

 number of teeth were normal. There were also other animals, related 

 to these last, which were, as made known by Marsh, the earliest rep- 

 resentatives, of the Horse family, who has recognized two genera of 

 them, Eohippus (meaning dawn-horse), and Orohippus (mountain- 

 horse). The latter belongs especially to the Bridger beds, but proba- 

 bly existed also in the Wahsatch. They were about as large as a 

 Fox. They had, in front, four perfect toes (Nos. 2, 3, 4, 5, out of the 

 normal five), and behind, three (Nos. 2, 3, 4), and the ulna and fibula 

 of the legs were free (see PJate X.) ; but they prove their close rela- 

 tion to the Horse-type in (1) the very deep oblique groove of the as- 

 tragalus or heel-bone for articulation with the tibia or lower bone of 

 the hind leg ; (2) the character of the teeth ; (3) the large diastema (or 

 toothless space) in the jaw in front of the premolars ; and (4) in the 

 elongated form of the feet. In Eohippus, the earliest form, there are 

 rudiments of a fifth toe in front (the inner or first). 



The even-toed Ungulates (characterized by having the toe No. 4 

 equal in all its articulations to No. 3, as to both size and strength, so 

 that the two strike evenly together, and by having the number of toes 

 usually two or four — these toes being Nos. 3 and 4, or Nos. 2, 3, 4, 5 

 (No 5 wanting in the hind foot of the Peccary)) were represented only 

 by species of the Hog family or Suillines (the genera, Eohyus, Para- 

 hyus). 



Besides species akin to the Ungulates, there were also Tillodonts 

 (Dryptodon Marsh) ; Monkeys, related to the Lemurs ; Carnivores 

 (genera Oxycena of Cope, Limnocyon of Marsh, etc.), related some- 

 what to the Wolf; and the earliest of Rodents, of the Squirrel type. 



In the next, or Bridger era, the Ungulates comprised other Tapir- 

 like species {Palceosyops, Hyrachyus, etc.) ; Horses of the genus Oro- 

 hippus; and new species and genera of Suillines (Helohyus, etc.). 



Another group is that of the Dinocerata of Marsh. These animals 

 were like Elephants in size, but rather short in legs, and bore on the 

 head three pairs of bony prominences standing out like the bases of 

 horns, one pair severally on the snout, the cheeks, and the forehead, 

 giving the huge beasts a grotesque rather than fierce aspect. In habits 

 they were probably like the Rhinoceros. They had five-toed feet like 



