264 TITANOTHERES CHAP, x 



Hyracodonts, and it is suggested that when swimming it was 

 raised above the surface as with the Hippopotamus. " This 

 feature," observes Professor Osborn, " with the long curved tusks, 

 undoubtedly used in uprooting, suggests the resemblance between 

 the habits of these animals and those of the hippopotami." There 

 were no horns in the Amynodonts. The face is shorter than in 

 the Hyracodonts, and the mastoid is covered as in recent Ehino- 

 ceroses. The canines are very strongly developed into tusks, but 

 the incisors show signs of disappearance. We know of the genera 

 Amynodon, Metamynodon, and Cadurcotherium. All except the 

 last, which is European, are American in range. 



Fam. 4. Titanotheriidae. These Oligocene Ungulates, often 

 attaining to large dimensions, are nearly peculiar, so far as is at 

 present known, to the North American Continent, and are at least 

 most abundant in it. 1 Many generic names, such as Titanotherium, 

 Erontotherium, Brontops, Titanops, and Menodus, have been given 

 to them ; but a recent study of the entire material accessible for 

 description or already described has led Professor Osborn to the 

 opinion that there was but a single genus, to which the name 

 Titanotherium must be applied. Of this genus there are some 

 thirty well-characterised species, of which the gradual evolution 

 can be traced from the lowest strata of the White River beds 

 where their remains occur. An entire skeleton of T. robustum 

 enables us to understand the osteology of these forms and to 

 compare them with other Perissodactyles. This animal was more 

 than 13 feet long, standing some 7 feet 7 inches in height. It 

 seems to have presented during life the aspect of a Ehinoceros with 

 perhaps a touch of Elephant. The skull is not unlike that of a 

 Khinoceros in general dimensions and shape ; but there are a pair 

 of apparent horn cores anteriorly, which are smaller in the more 

 ancient forms and acquire a large size, a forward direction with a 

 divergence of the two in the later forms. A glance at the 

 accompanying figures of skulls (Fig. 137) of early and later 

 Titanotheres will exhibit the changes in this particular which the 

 skulls underwent in the lapse of time occupied by the deposition 

 of these Oligocene beds. The nasals are short in the later, longer 

 in the more early species, such as T. heloceras and T. coloradense. 

 The zygomatic arch projects much, and is " shelf-like " in the 

 later forms, the skull thus getting an immense breadth, which, 



1 Remains of the genus have been met with in the Balkans. 



