ORDER UNGULATA. 



1317 



gated ; and 

 formula is 



the orbits are tubular and very prominent. The dental 



j (2_3) c p m 4 M 3 The c heek-teeth are 

 (i-3) 1 4 3 



bunodont in structure; the true molars (fig. n 89) having four 

 columns, which present trefoil-shaped dentine surfaces when worn ; 

 the premolars are simpler. The upper incisors are short and ver- 

 tical (fig. 1 187), but those of the lower jaw are procumbent, and 

 may be very large (fig. 1191). The canines of the upper jaw are 

 curved upwards like those of pigs, while the lower ones are of 

 enormous size, and have their extremities obliquely worn to a cutting- 



Fig. 1 190. —Hippopotavms sivalensis ', from the Pliocene of the Siwalik hills, a, Palatal 

 view of cranium; b, Third right upper true molar ; c, Symphysis of mandible. Reduced. 



edge by biting against the outer surfaces of those of the upper jaw. 

 The feet (fig. 1188) are short and massive, and furnished with four 

 digits, of which the terminal phalangeals bear nail-like hoofs. The 

 skin is nearly naked and of great thickness ; while the ears and 

 eyes are very small, and the tail is short. 



In the more generalised forms like H. sivalensis (fig. 1190), of the 

 Pliocene of the Siwalik Hills of India, there are three pairs of incisors in 

 both jaws, all of which are of subequal size. This hexaprotodont group 

 is represented in the Pliocene of Burma by H. iravaticus, and in that of 

 Algiers by H. bonariensis ; while its latest member is H. ?iamadicns, of 

 the Pleistocene of the Narbada Valley, in India. In the latter deposits 



