30 ELEPHANTS. 



skull, and, although its upper surface is still deeply grooved and 

 spout-like as in the earlier forms, the lower incisors no longer 

 meet in the middle line and prolong the spout, but are rounded, 

 directed downward, and separated from one another. In this 

 animal it is clear that the lower jaw was shortening np and could 

 no longer reach the ground, but doubtless the fleshy upper lip 

 and nose, now freed from their bony support for at least part 

 of their length, became flexible and better adapted for grasping 

 the animal's food. In fact, this species must have looked much 

 the same as a modern elephant, except that it had a longer chin 

 bearing a pair of small downwardly directed tusks. 



In some of the American Tetrabelodons of about the same 

 age as T. longirostris, the lower tusks, instead of undergoing 

 reduction, seem to have become greatly enlarged, and at the 

 same time the symphysial portion of the mandible is slightly 

 deflected, so that the mandible with its tusks is to some degree 

 similar to that of Dinotherium. An example of this form of 

 jaw is seen in the case of the mandible of a Tetrabelodon 

 (T. dinotherioides) from the Loup Fork Beds (Upper Miocene) 

 of Kansas, exhibited in Pier-case 42 (fig. ] 7) . 



DINOTHERIUM. 



Tetrabelodon dinotherioides has no near relationship with 

 Dinotherium (fig, 18) (Wall-case 43 ; Case C), which forms a 

 side branch of the Proboscidea, and is widely different from 

 all the other members of the group. The earliest-known 

 member of the genus is Dinotherium cuvieri, a comparatively 

 small animal, which is found in the same deposits as the earliest- 

 known remains of Tetrabelodon angustidens, and, as in the case 

 of that species, its ancestors probably lived in Africa, though up 

 to the present no traces of them have been discovered. In the 

 later Miocene beds occur a number of species, some of enormous 

 size (e. g., D, gigantissimum from Roumania). The genus finally 

 disappears in Lower Pliocene times. The chief peculiarity 

 of these animals is that the front part of their lower jaw is 

 turned sharply downward and bears two large tusks (fig. 18, 

 Case C) ; probably there were no tusks in the upper jaw. The 

 skull js remarkable for the great expansion of the occipital 



