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PTERYGOID.EUS EXTERNUS. 23
Lower-Jaw ; lying, as it were, horizontally along the basis of
the Skull. It is somewhat radiated in some bodies ; broad at
the origin, and small at the insertion ; but the greater part of

adult male Orang {Pith. Satyrus). In other specimens of this species,
the parietal ridges, although considerahly developed, are not blended
together in the form of a median crest, hut are separated by an interval
of varying width. These differences in the crania of the male Orangs
do not seem to indicate a difference in race ; they are rather the indices
In the males of Loth Tr. Gorilla and
of age and muscular energy. (1)
Pith. Satyrus the laniaries attain a development almost rivalling their
proportions in the more powerful Carnivora. In the females of these
species, on the othei hand, which are distinguished by the compara-
tively small size of the canines, the osseous cristse are proportionately
of minor development ; the parietal ridges do not unite to form a high
sagittal crest, but are continued separately backwards over the upper
surface of the cranium, albeit in the female Gorilla they are only
Again, in the smaller species of Chim-
divided by a narrow groove. (2)
panzee (Tr. nigcr) the muscular processes of the male skull are less
developed than in Tr. Gorilla, the laniaries also attaining smaller
dimensions. But in all these great Apes it is only on the completion
of the second dentition that the surface for the attachment of the biting
muscles becomes thus extended. In the immature Chimpanzees and
Orangs, whilst the cranial portion of the skull is comparatively large,
the facial part and especially the jaws are but little developed, the sur-
face of the cranium is uninterrupted, and the temporal fossae lack the
depth which they afterwards acquire, with the full attainment of the
powers of combat and mastication. It is at this stage of his existence
that the young Ape is so eminently anthropoid : but, "as growth pro-
ceeds, the milk teeth are shed, the jaws expand, the great canines suc-
ceed their diminutive representatives, the biting muscles gain a propor-
tional increase of carneous fibres, their bony fulcra respond to the call
for increased surface of attachment, and the sagittal and occipital crests
begin to rise." (3)
It is scarcely necessary to say that no such extension of the temporal
fossa is ever found in Man ; although in the low, uncivilized races, where
the teeth and jaws are put to rough work, it is not unusual to find the
arched border of the fossa more strongly defined than in the higher
(1) Vide Owen, Zool. Trans., vol. iv., p. 165.
(2) Descriptive Catalogue of Osteological Scries in Museum of R. Col. of
Surgeons, vol. ii., p. 803.
(3) Owen, Class, and Distrib. Mammalia, Appendix on Gorilla, p. 76.