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24 PTERYGOID^US EXTERNUS.
it forms a round strong fleshy belly ; so that the part that makes
it of the radiated kind is thin.

varieties. In both Man and the Quadrumana the zygoma is slightly
curved outwards ; amongst the latter the outward curve is well marked
in the Baboons (Cynocephali).
It is in the order Carnivora that the temporal acquires its highest
development. This is evidenced by the great depth of the
fossa, the
outward curve of the zygoma, the development of frontal, parietal, and
occipital crests, and the height of the coronoid process of the lower jaw,
The skulls of the
together with its deeply-excavated external surface.
hyaena, wolf, and some of the larger kinds of dog—e. g., the mastiff,
blood-hound, &c—are remarkable for the development and height of the
sagittal crest, produced by the union of the frontal and parietal ridges.
Amongst the Felidce, the single crest is best expressed in the cranium of
the lion ; in the smaller species the parietal ridges only meet in the
posterior part of their extent. On removing the skin from the upper
surface of the head in these animals, we find nothing on each side
but the great mass of the temporal, which completely covers the
superior and lateral regions. In the Cat, the muscle is described by
Straus-Durckheim as consisting of three portions—an antero-external
of large size, which arises from the anterior part of the strong
temporal aponeurosis and the anterior part of the fossa, and two
posterior portions, of which the internal is the larger, and occupies the
two posterior thirds of the same fossa. The three heads unite to be
inserted into the coronoid process of the jaw, their fibres covering its
surfaces and borders, being attached on the inner side as low down as
the dental foramen, on the outer to the upper portion of its surface,
If
and to an aponeurosis common to this muscle and the masseter. (1)
we contrast with the Carnivora the Ruminants and Rodents, we find
a wide difference in the development of the temporal, as indicated by
the size and depth of its fossa. In the latter orders this space is narrow
and shallow, the muscular ridges are but slightly expressed ; and in the
Ruminants the zygomatic arch is short, and projects but As
little. (2)
another instance of the close relation which exists between the develop-
ment of the temporal muscle and the dental type, we may adduce the
Camel. In the Camel, canines are present in both jaws, together with a
pair of laniarifonn incisors and premolars in the upper jaw. Concomitant
on this higher type of dentition, we find the skull furnished with a sharp
and deep but thin occipital crest, a low but sharp parietal crest,
(1) Vide Straus-Durckheim, Anatomic Descriptive et Comparative du
Chat, T. ii., p. 210.
(2) Cuvier, op. cit., lccon xvi.