the canine of a horse. Castration arrests the development of the
tusks in the male.
The teeth of the molar series progressively increase in size
from the first to the last : the first premolar (PI. 140, fig. 1, p 1)
has a simple compressed conical crown, thickest behind, and has
two fangs: it is further removed from the second in the Sus
larvatus than in Sus scrofa. The second premolar (ib. p 2) has a
broader crown, with a hind-lobe, having a depression on its inner
surface ; and each fang begins to be subdivided. The third premolar
(ib. p 3) has a similar but broader crown implanted by four fangs.
The fourth premolar (ib. p 4) has two principal tubercles and
some irregular vertical pits on the inner half of the crown. In
the masked Boar the third upper premolar is larger, thicker, and
more pointed than in the common Boar. The first true molar, when
the permanent dentition is completed, exhibits the effects of its early
development in a more marked degree than in most other Mammalia,
and, in the Wild Boar, has its tubercles worn down, and a smooth
field of dentine exposed by the time the last molar has come into
place (PI. 141, fig. 3, m 1): it originally bears four primary cones,
with smaller subdivisions formed by the wrinkled enamel, and
an anterior and posterior ridge. The four cones produced by the
crucial impression, of which the transverse part is the deepest,
are repeated on the second true molar (ib. m 2) with more complex
shallow subdivisions and a larger tuberculate posterior ridge. The
greater extent of the last molar (ib. m 3) is chiefly produced by
the development of the back ridge into a cluster of tubercles :
the four primary cones being distinguishable on the anterior main
body of the tooth. The hind lobe is more simple and smaller in
the masked than in the common Boar. There is generally a small
tubercle at the outer and inner interspace between the two
principal lobes of the true molars. The number of fangs increases
with the increasing size of the crown.
The crowns of the lower molars are very similar to those
above, but are rather narrower, and the outer and inner basal
tubercles are much smaller or are wanting. The transverse
depression on the first and second true molars is deeper in the
lower than in the upper jaw; its borders of enamel are very
sinuous; in the second true molar each anterior lobe is penetrated
by a secondary fold at its posterior margin, and the posterior
division is divided into three lobes, the enamel coats of which
form three islands arranged in a triangle when the surface is
worn down to a certain extent: the last molar is divided by
two transverse depressions into three principal lobes, the last
being the longest in the common Hog, and the shortest in the
Masked Hog; the two anterior divisions are each subdivided by
the longitudinal furrow into two tubercles, and these are broken
by many secondary depressions into smaller tubercles. The inferior
canines of the Wild Boar are longer, and curve upwards, outwards,
and backwards, in a more normal direction than those
above: they are three-sided; the broadest convex side is directed
obliquely inwards and forwards ; the outer and posterior sides are
nearly flat; the latter surface has no enamel, and the tusk wears
obliquely from behind, upwards and forwards to a point, with two
sharp enamel edges. Both upper and lower canines have the
characters of true tusks in the projection of their crown beyond
the lips, and their insertion by a long undivided and undiminished
base, widely excavated for a persistent matrix which ensures the
uninterrupted growth of these formidable weapons. Each tusk in
a lower jaw of one foot in length, from a German Wild Boar,
measures eight inches along its curve : but tusks of twelve
inches in length have been obtained from the Wild Boars of
Assam.
The smaller species of Asiatic Hog, called Babiroussa, has
obtained from the extraordinary development and direction of its
tusks the name of ‘ homed Hog’ (PI. 140, fig. 3) ; and both molar
and incisor teeth offer some varieties from those of the ordinary
species of Sus. The incisors are reduced to four in number in
the upper jaw by the early loss of the two small outer ones; the
first and second, on each side, which remain, correspond in form
with those of the common Hog. The six incisors are retained in
the lower jaw. The upper canines are more slender than in the
N N 2