ks both in the upper and lower jaw,
and the more anterior grinders have become quite minute. The cats
(lions and tigers included) have kept the full number of incisors (see
Figs. 21 and 22, pp. 103, 104); they have developed the four canines
into enormous and deadly stabbing "fangs," and they have lost all the
grinders but three in each half of the lower jaw and four in each half
of the upper jaw (twelve instead of twenty-eight), and these have
become sharp-edged so as to be scissor-like in their action, instead
of crushing or grinding. Man and the old-world monkeys have lost an
incisor in each half of each jaw (see Pls. VI and VII); they retain
the canines, but have only five molars in each half of each jaw
(twenty in all instead of twenty-eight). Most of the mammals--whatever
change of number and shape has befallen their teeth in adaptation to
their different requirements as to the kind of food and mode of
getting it--have retained a good long pair of jaws and a snout or
muzzle consisting of nose, upper jaw, and lower jaw, projecting well
in front of the eyes and brain-case. Man is remarkable as an
exception. In the higher races of men the jaws are shorter than in the
lower races, and project but very little beyond the vertical plane of
the eyes, whilst the nose projects beyond the lips. Another exception
is the elephant. This is most obvious when the prepared bony skull and
lower jaw are examined, but can be sufficiently clearly seen in the
living animal. The lower jaw and the part of the upper jaw against
which it and its grinders play is extraordinarily short and small. The
elephant has, in fact, no projecting bony jaw at all, no bony snout,
its chin does not project more than that of an old man, and even the
part of the upper jaw into which its great tusks are set does not bend
forward far from the perpendicular (Fig. 9).

[Illustration: Fig. 11.--A reconstruction of the extinct American
mastodon (_Mastodon ohioticus_) from a drawing by Prof. Osborne. Other
extinct species of mastodon are found in Europe.]

[Illustration: Fig. 12.--A. Skull, and B. restored outline of the head
of the long-jawed extinct elephant called Tetrabelodon--the name
referring to its four large tusks--two above and two below.]

The elephant (see Fig. 9) has no sign of the six little front teeth
(incisors) above and below which we find in the typical dentition and
in many living mammals, nor of the corner teeth (dog-teeth, or
canines). In