HIGH SCHOOL ZOOLOGY. 175 



represented by one or two species in the rivers of Africa. Their denti- 

 tion is singular, for although the milk teeth are if, c}, na^, the adults 

 have only if, c^, nig, there being no permanent successors for one of the 

 milk incisors and one of the milk molars. The peraiauent front teeth 

 are tusk-like, the incisors being straight, ■while the canines are curved, 

 and meet each other in such a way, that the posterior faces of the much 

 larger lower ones are ground flat against the anterior faces of the upper 

 ones. 



The second family has many more representatives, and a much less 

 limited geographical distribution, for there are several Old AVorld 

 genera, as well as the Peccaries, which are peculiar to the New World. 

 The skin in all is more or less closely beset with bristles, their bodies 

 are more elongated, and thus better adapted for rapid locomotion, and 

 they are sujjported solely by the third and fourth toes ; the second 

 and fifth, although they are complete and furnished with hoofs, not 

 reaching the ground. (Fig. 115 — A.) 



The Peccary even oflfers a further reduction in the hind foot, for 

 the fifth toe there is undevelopecL This genus (Dicotyles) is in 

 many respects the most specialised of the family, for apart from 

 the structure of the hind foot, and a reduction in the number of incisors 

 and molars, the stomach resembles in its complexity that of the 

 Ruminants. On the other hand, the genus .SV(.s is the most primitive, for 

 its dentition is if, Cy, pra|, mf, whereas in the other genera, there is 

 either a reduction in the number of the incisors or molars, or both. 

 The canines are generally tusk-like, the lower ones being fhe chief 

 weapons in the family, but the upper ones may also attain a formid- 

 able size, as in the pig deer — Babyrussa — of the Moluccas [Porcus), 

 where they are curved upwards and backwards; the incisors are small 

 and sometimes absent in the adult, as in the pigmy hog (Porcula) of 

 India, and the wart-hog (Phacochozrus) of Africa, but the molars are 

 always of a tuberculate pattern. 



30. The foregoing families constitute the non-ruminant sec- 

 tion of the Artiodactyla; all the othei* numerous genera are 

 ruminaiit forms, the stomach being complex, so as to admit of 

 their characteristic way of feeding. This and the reduction of 

 the second and fifth toes are both to be regarded as subservient 

 to the more rajiid locomotion in this group, for these herbivora, 

 which are the chief objects of pursuit by the larger carnivores, 



