282 UNGULATA 
but curving strongly outwards, upwards, and finally inwards, while 
those of the lower jaw are directed upwards and outwards with 
a gentle backward curve, their hinder edges working and wearing 
against the front edges of the upper canines! They appear 
externally to the mouth as tusks, the form of the upper lip being 
modified to allow of their protrusion, but are much less developed 
in the females than in the males. The teeth of the molar series 
gradually increase in size and complexity from first to last, and 
are arranged in contiguous series, except that the first lower 
premolar is separated by an interval from the second. First and 
second upper premolars with compressed crowns and two roots. 
The third and fourth have an inner lobe developed on the crown, 
and an additional pair of roots. The first and second true molars 
have quadrate crowns, with four principal obtuse conical cusps, 
around which numerous accessory cusps are clustered. The length 
of the third molar is nearly equal (antero-posteriorly) to that of 
the first and second together, its crown. having, in addition to the 
four principal cusps, a large posterior talon or heel, composed of 
numerous clustered conical cusps, and supported by several additional 
roots. The lower molar teeth resemble generally those of the upper 
jaw, but are narrower. Milk dentition: 73,¢4,m3; total 28,— 
the first permanent premolar having no predecessor in this series. 
The third incisor, in both upper and lower jaws, is large, developed 
before the others, and has much the size, form, and direction of 
the canine. Vertebre: C7,D13-14, L 6,8 4, C 20-24. The hairy 
covering of the body varies much under different conditions of 
climate, but when best developed, as in the European Wild Boar, 
consists of long stiff bristles, mostly abundant on the back and 
sides, and of a close softer curling under-coat. 
The skull of the Pigs (Figs. 103-105) has the axis of the face 
bent down upon the basicranial axis, as is also the case with the 
Sheep. Its most striking feature is the elevation and backward 
slope of the occipital crest formed by the union of the supraoccipital 
and parietals. The broad and flat frontals have small postorbital 
processes, which do not join the zygomata, so that the orbits are 
open behind. The nasals are very long and narrow; and the pre- 
maxille send up long nasal processes, stopping short of the frontals. 
A peculiar prenasal bone is developed at the anterior extremity of 
the mesethmoid, which serves to strengthen the cartilaginous snout. 
The palate is long and narrow, and extends behind the last molar 
1 If from any accidental circumstances these teeth are not constantly worn 
down by friction, they grow into a complete circle, the point penetrating the 
bone of the jaw close to the root of the tooth. The natives of the Fiji Islands 
avail themselves of this circumstance to produce one of their most valued orna- 
ments—a circular boar’s tusk: the upper canines being extracted, the lower ones 
are allowed to grow to the desired form. 
