356 MR. R. OWEN ON THE OSTEOLOGY OF 
In the course of this comparison it will be shown that the number and value of the 
points of resemblance or of approximation to the Bimanous structure are in favour 
of the Chimpanzee ; and that, as in many similar instances, there are some particulars 
of the organization of the Orang which indicate a closer affinity with the inferior forms 
of the group to which it belongs than to those Quadrumana which rank immediately 
below it. 
Notwithstanding the many strongly marked characters which the cranium of the adult 
Orang exhibits in common with that of the Mandrill, as the contracted forehead, the 
flattened occiput, the formidable canine teeth, huge jaws, strong expanded zygomatic 
arches, and largely developed cranial ridges, yet in continuing the comparison we can- 
not fail to be struck with the general effect of a less ferocious expression in the skull of 
the Orang. This results from the more perpendicular slope of the facial contour, from 
the absence of the projecting superciliary ridges (beneath which even the sightless 
sockets of the Mandrill scowl upon the observer), from the greater expansion of the 
cerebral cavity, and lastly, from the non-development of the superior maxillary ridges, 
which appear in the Mandrill as a gratuitous supplement to the hideous tout ensemble of 
its head. 
The cranium of the Orang is less flattened at the crown than that of the Chimpanzee. 
The size of the cavity of the skull exceeds in a very small degree that of the young 
animal at the period when it has acquired the first permanent molares, the subsequent 
enlargement of the cranium being chiefly owing to the thickening of its walls and to the 
development of the muscular ridges which circumscribe the origins of the temporal mus- 
cles. These ridges commence at the external angular process of the frontal bone, pass 
inwards, upwards, and backwards behind the superciliary ridge, from which they are 
separated by a deep groove, then, converging upon the cranium, they meet at the junc- 
tion of the sagittal with the coronal suture, including a neat triangular portion of the 
frontal bone, along the middle of which there is a slight longitudinal convexity. The 
smoothness of this part of the cranium forms a contrast to the irregularly indented sur- 
face of the remainder, which is exclusively the seat of origin or attachment of powerful 
muscles. 
The interparietal crest rises, as in the Hyena and other Carnivora, above the ge- 
neral level of the skull, to the extent of from 4 to = of an inch; at the verte it divides 
and passes posterior to the lambdoidal suture to the mastoid ridge. A third strong 
spine is continued from the point of divarication half way down the squamous portion 
of the occiput, and forms a strong posterior projection at its commencement. The 
situation of these ridges in reference to the sutures, is only determinable by comparing 
the faint commencement of their growth in the young Orang’s skull. In two adult 
skulls, where the ridges were fully developed, the only traces of the cranial sutures 
which were visible were the upper part of the squamous, about 1 inch of the lower 
end of the coronal, and that small one by which the ala of the sphenoid joins the 

