in, grass or herbage to a paste, as
are those of the goat (Fig. 17), those of the Coypu rat (Fig. 19), and
those of the elephants and mastodons (Fig. 8).]

[Illustration: Plate VII.--Drawings of (1) the upper and (2) the lower
series of teeth of the Gibbon (_Hylobates concolor_), one of the
anthropoid or most man-like apes (enlarged by one third). If these
drawings are compared with those in Pl. VI, showing man's teeth, the
most striking difference seen is that the "arch" or series of teeth is
here elongated and squared, not rounded in front, whilst there is
plenty of room in both jaws for the last or wisdom tooth, which is not
the case in modern races of men, though in the ancient Neander man's
jaw and in that from Heidelberg there is ample space for the last
molar as in the apes. The next most important difference is that in
the gibbon the four canine teeth are very large and tusk-like, and
must certainly be of value as weapons of attack--which man's are not.
Connected with the large size of the canines is the presence of a gap
(or "diastema" as it is called) between the four front teeth or
incisors of the upper jaw and the upper canine--which allows the lower
canine to fit in front of the upper canine when the jaw is closed. The
number of the tubercles or cones on the molars (the two smaller
pre-molars and the three hinder large molars) can be compared in
detail in these beautiful drawings from Professor Selenka's work,
which are the most careful and perfect which have ever been published.
The agreement of these teeth in man and the gibbon is very close: but
there are differences. The first, or most anterior pre-molar of the
lower jaw has one predominant cusp or cone; the second, like both in
the upper jaw, is "bicuspid," or bi-tuberculate, as in man. The three
big molars of the upper jaw are closely similar to those of man, with
some small differences, the second being quadri-tuberculate, whilst in
man it is as often tri-tuberculate (as it is in Pl. VI) as it is
quadri-tuberculate. But the two anterior big molars of the lower jaw
are seen to have each five well-marked cones, cusps or tubercles; they
are quinqui-tuberculate, whilst in man the first lower molar is often
quadri-tuberculate and the second even more frequently so. The last
lower molar (wisdom tooth) of the gibbon is like that of man,
quadri-tuberculate.

The details of the tubercles on these molar teeth distinctly justify
the conclusion that they are a