TERTIARY AGE. 505 



the Coryphodonts, to which they were somewhat related. The spe- 

 cies are referred to three genera : Uintatherium of Leidy (named from 

 the Uinta Mountains) and Dinoceras and Tinoceras of Marsh. On 

 Plate VIL, Figs. 1 and 2 sliow the skull in different positions, and the 

 former also the size of the little brain (b) ; and Figs. 3, 4, a fore-foot 

 and hind-foot. The name Dinoceras, from the Greek Seu/os, terrible, 

 and Kepa?, horn, alludes to the three pairs of prominences (Figs. 1, 2). 

 In some of the Dinocerata, as the Uintatherium Leidyanum of Osborn, 

 Scott and Speir, the prominences are long and look like horns. It is 

 supposed that part, if not all, of them were horn-cores or bases of 

 horns ; any not so must have been covered with the hide as in the 

 Giraffe. While thus armed to excess, and probably of great strength, 

 the very small brain shows that they were extremely low in intelli- 

 gence. 



The Tittodonts were another group peculiar to the Eocene. In the 

 Wahsatch group occur remains of the earliest species. In the Bridger, 

 there are other kinds ; and one genus of them was named Tillotherium 

 by Marsh. The name, from tl\A.w, to bite, alludes to the long incisors 

 or front teeth, which are only two in number, and long, much as in the 

 Beaver (Castor Canadensis) and other Rodents, and which give the 

 animals a Rodent-like aspect. The earliest known of the Bridger 

 group of Tillodonts was called by Leidy Trogosus Castoridens, in allu- 

 sion to this resemblance in the teeth; he afterwards identified it with 

 a New Jersey Eocene species, his Anchippodus riparius. Fig. 1, on 

 Plate VIII., shows the form of the skull, with the small brain ; Fig. 

 2, a profile view of the same with the lower jaw ; Figs. 3, 4, upper and 

 lower molars, and 5, a, b, the claws. 



The Bridger era had also monkeys related to the Lemurs, Car- 

 nivores related to the Fox, the Wolf, and the Cat, the largest nearly 

 equaling the Lion in size ; Bats, Squirrels, among Rodents ; and Moles 

 among Insectivores. 



The Uinta group, the last of the Eocene, has afforded new Tapir- 

 like species (the Diplacodon related to Palceosyops of the Bridger 

 group), species of the oldest known genus of the Rhinoceros group 

 (Amynodon) ; and also new even-toed Ungulates (Parameryx, Orome- 

 ryx, etc.) that had some relations to the Camels and Stags, and were 

 the precursors of the true Ruminants. 



(2.) Miocene. — The Miocene Mammals were of different species, 

 and mostly of different genera from the Eocene. There were new 

 Tapir-like kinds, some of them referred to the genus Lophiodon, which 

 had also European species ; new Horses of the genera Mesohippus, 

 Miohippus, and Anchitherium, having but three toes in front, and the 

 ulna and fibula not free (Plate X.) ; several new genera of the Hog 



