400 PROFESSOR OWEN ON THE OSTEOLOGY OF 



Viewed from before, the enormous supraorbital arch witli the tumid malar bones 

 again form tlie most striking characteristic of the Chimpanzee : the orbits are sub- 

 quadrate with the angles rounded off; in the Orang they are full ellipsoids with the 

 long diameter vertical. The zygomata are more directly continued backwards from 

 the malars, which contribute a larger proportion to the arch in the Chimpanzee, whilst 

 in the Orang they curve more outwards. The flat and narrow nasal of the Orang 

 contrasts strongly with the form of the same bone, which is prominent above and 

 expanded below, in the Chimpanzee ; and the oval nostril, contracted above in the 

 Orang, equally contrasts with the full elliptic nostril in the Chimpanzee. The alveolar 

 portion of the premaxillaries is longer in the great Orang than in the great Chimpanzee, 

 and, with the canine-alveoli, this part of the face is broader as well as more prognathic 

 in the great Orang. The malar process of the maxillary is shorter in the Orang ; it is 

 more deeply impressed outside the socket of the canine, and the inferior angle at its 

 junction with the malar is more produced downwards : the suborbital outlet is more 

 constantly divided into two or three foramina in the Orang. 



In the basal view the occipital region is both broader and flatter in the great Chim- 

 panzee ; it approaches Man nearer in the minor degree of its inclination from the 

 horizontal plane of the basis cranii, in the more advanced position of the condyles and 

 zygomatic arches, by the shorter extent of the basioccipital and basisphenoid, and by 

 the greater concavity of the glenoid fossae for the lower jaw. The occipital condyles 

 are less convex in the Chimpanzee and somewhat smaller than in the Orang ; they 

 appear therefore disproportionately small as compared with the size of the skull, which 

 is poised by them upon the atlas. The basioccipital is narrower and more convex an- 

 teriorly in the Chimpanzee. 



The precondyloid foramen, which is usually single in the Chimpanzee, opens imme- 

 diately below — almost into — the jugular foramen; whilst in the Orang, in which there 

 are usually two precondyloid holes, the exoccipital extends forwards and outwards a 

 quarter of an inch beyond them before it forms the posterior border of the jugular 

 foramen. 



The processus jugularis of the exoccipital is longer and more curved forwards in the 

 Orang, and the rough ridge representing the paroccipital process is better developed : 

 the form and extent of the jugular process {j p, PI. LXIII.) in the Chimpanzee is more 

 like that in Man. 



The angular process of the petrosal [p j) encroaching upon the foramen jugulare is 

 more developed in the Chimpanzee, and more resembles that in Man. 



The carotid foramen is more oblique, being defended by a ridge along its outer side 

 in the Chimpanzee answering to that continued from the vaginal process in Man ; there 

 is no such ridge in the Orang. 



The eustachian process (e) of the petrosal is much thicker and less sharply pointed in 

 the Chimpanzee ; the apex of the petrosal itself is also thicker and less pointed. 



