_Sus._[178]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Upper incisors diminishing rapidly in size from the first to the third. Lower incisors long, narrow, closely approximated, and almost horizontal in position, their apices inclining towards the middle line; the second slightly larger than the first, the third much smaller. Canines strongly developed and with persistent roots and partial enamel-covering, those of the upper jaw not having the usual downward direction, 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[179]. 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: _i_ ³⁄₃, _c_ ¹⁄₁, _m_ ³⁄₃; 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. Vertebræ: C 7, D 13-14, L 6, S 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 undercoat.