Its maximum of production, however, is met with in the genus Chrysothrix. The convexity of the occiput is well marked in Simia, Troglodytes niger, and Hylobates, while in the inferior Simiadae it is flat. It is in American forms, especially in the genus Pithecia, that we find the greatest resemblance to man in this respect but the skiull is lofty in the orang. No ape, especially no ape of the Old World, presents to elevated and rounded a contour in the frontal region as does man. The relation of the face to the cranium (or brain case) is best shown by the craniofacial angle, which is estimated by means of two lines, one drawn parallel to the base of the skull (from the front margin of the occipital foramen to the anterior end of the cerebral surface of the presphenoid), the other drawn from the front end of that base to the middle of the lower margin of the upper jaw. In the Cebidae the facial part is relatively smaller than in the Simiadoe, with the exception of Mycetes, while in Chrysothrix the facial portion of the skull is relatively smaller than even in man himself. Thus the facial part is already very large in the orang and chimpanzee, much more so than in Semnopithecus, where most of the ape cranial characters are moderately developed, or even than in many Cercopitheci but it attains its maximum of relative size in the Cynocephali, above all in C.
#GORILLA SKULL MASTOID PROCESS SERIES#
This proportion also varies in an irregular manner as we descend (through the series of apes) from those which are most like man. The proportion of the latter portion to the former varies greatly from age and sex, owing mainly to the differences produced through the development of large and powerful canine teeth in the adult males of most species. The artificial division of the skull into a cranial and a facial portion may be here conveniently adopted from human anatomy.
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