288 UNGULATA 
entirely devoid of hair. With regard to the curiously modified 
dentition, Wallace (Malay Archipelago, vol. i. p. 435) makes the 
following observations: —‘“It is difficult to understand what can 
be the use of these horn-like teeth. Some of the old writers 
supposed that they served as hooks by which the creature could 
rest its head on a branch. But the way in which they usually 
diverge just over and in front of the eye has suggested the more 
probable idea, that they serve to guard these organs from thorns 
and spines while hunting for fallen fruits among the tangled thickets 
of rattans and other spiny plants. Even this, however, is not 
satisfactory, for the female, who must seek her food in the same 
way, does not possess them. I should be inclined to believe 
rather that these tusks were once useful, and were then worn 
down as fast as they grew, but that changed conditions of life have 
rendered them unnecessary, and they now develop into a monstrous 
form, just as the incisors of the Beaver and Rabbit will go on 
growing if the opposite teeth do not wear them away. In old 
animals they reach an enormous size, and are generally broken off 
as if by fighting.” 
Phacocherus1—The Wart-Hogs, so called from the large 
cutaneous lobes projecting from each side of the face, have 
the teeth still more remarkably modified than in Babirusa. 
The milk-dentition, and even the early condition of the per- 
manent dentition, is formed on the same general type as that 
of Sus, except that certain of the typical teeth are absent, the 
formula being 7 4, ¢ +, p 3, m %, total 34; but as age advances all 
the teeth have a tendency to disappear, except the canines and the 
posterior molars, which in some cases are the only teeth left in 
the jaws, and attain an extraordinary development. The upper 
canines especially are of great size, and curve outwards, forwards, 
and upwards. Their enamel covering is confined to the apex, and 
soon wears away. The lower canines are much more slender, but 
follow the same curve ; except on the posterior surface, their crowns 
are covered with enamel. Unlike those of the Babirusa, the canines 
of the Wart-Hog are large in both sexes. The third molar tooth of 
both jaws is of great size, and presents a structure at first sight 
unlike that of any other mammal, being composed of numerous 
(22-25) parallel cylinders or columns, each with pulp-cavity, dentine, 
and enamel covering, and packed together with cement. Careful 
examination will, however, show that a similar modification to that 
which has transformed the comparatively simple molar tooth of 
the Mastodon into the extremely complex grinder of the Indian 
Elephant has served to change the tooth of the common Pig into 
that of Phacochwrus ; and, as already mentioned, some of the fossil 
Indian and African species of Sus indicate the mode in which this 
? Cuvier, Regne-Animal, vol. i. p, 236 (1817). ° 
