In Insectivorous Bats the skull is generally shorter and broader than in the Pteropidae. The cranial cavity is large and rounded, and has thin smooth walls. The zygomatic arch is slender, and postorbital processes are not generally well developed. The premaxillae is generally small, sometimes absent. The tympanics are ring-like and are not connected with the surrounding bones. The angle of the mandible is distinct. The hyoid in most respects resembles that of the Insectivora. PRIMATES. The characters of the skull differ greatly in the two suborders of Primates, the Anthropoidea and the Lemuroidea. In the _LEMUROIDEA_ the general relative proportions of the cranium and face are much as in most lower mammals, and the occipital plane forms nearly a right angle with the basicranial axis. The postorbital processes of the frontals are commonly continued as a pair of ridges crossing the roof of the cranium and meeting the occipital crest. Though the postorbital bar is complete, the orbit and temporal fossa communicate freely below it. The lachrymal canal opens outside the orbit, and the lachrymal forms a considerable part of the side of the face. The tympanic is developed into a large bulla. The hyoid apparatus much resembles that of the Dog. In the _ANTHROPOIDEA_ the skull differs greatly from that in the Lemuroidea. The cranial portion of the skull is very large as compared with the facial portion, though the comparative development varies, some monkeys, such as the baboons (Cynocephali) having the facial portion relatively large. The comparative size of the jaws does not vary inversely with the general development of the animal, some of the Cercopithecidae having comparatively larger jaws than some of the Cebidae. The great size of the cranial part of the skull is mainly due to the immense development of the cerebral fossa, which commonly completely overlaps the olfactory fossa in front, and the cerebellar fossa behind. This development also has the effect of making the ethmoidal and occipital planes lie, not at right angles to the basicranial axis, but almost in the same straight line with it. This is, however, not always the case, as the Howling Monkey (_Mycetes_) and also some of the very highest monkeys, the Gibbons (_Hylobates_), have the occipital plane nearly vertical to the basicranial axis. In adult Man the basi-occipital, exoccipitals and supra-occipital coalesce, forming the so-called occipital bone; while the basisphenoid, presphenoid, alisphenoids, orbitosphenoids and pterygoids form the sphenoid bone. The roof of the skull is partly formed by the large supra-occipital and frontals, but mainly by the parietals (fig. 99, 1), which in Man are of enormous extent. [Illustration FIG. 99. HALF FRONT VIEW OF THE SKULLS, _A_ OF AN OLD, _B_ OF A YOUNG GORILLA (_Gorilla savagei_) × 1/4. (Camb. Mus.)