198 



QUADRUMANA. 



towards the anterior part, which is, as it were, 

 truncated. The cerebral portion, or the cra- 



Fig. 116. 



Skull of Simla troglodytes. (After Owen.') 



mum, is smooth, and convex on its superior 

 or coronal aspect, being devoid of the inter- 

 muscular frontal and sagittal crests, which 

 give so strong a carnivorous character to the 

 skull of the Orang-oetan. For the insertion 

 of the temporal muscle there is, however, a 

 long boundary continued from the outer part 

 of the supra-orbital ridge, at first as a well- 

 marked crest, but soon becoming a slightly 

 elevated line, which is lost in the lambdoidal 

 and supra-auditory ridges. The coronal su- 

 ture has a transverse direction ; the occipital 

 foramen is further from the posterior plane 

 of the cranium, and its position is less oblique 

 than in the Orang-cetan. Consequently there 

 is a greater proportion of brain behind the 

 meatus auditorius externus in the Chimpanzee 

 than in the Orang-oetan. Behind the condyle 

 of the lower jaw there is, in the glenoid cavity 

 of the temporal bone, a process, of which the 

 rudiment exists also in man, affording a sup- 

 port for the jaw to guard against a backward 

 dislocation. The frontal bone is single as in 

 man, but distinguished by large projecting 

 supra-orbital ridges, which form a sort of line 

 of demarcation between the cranium and the 

 face. The squamous portion of the occipital 

 bone is of considerable extent, more convex 

 than in the Orang, and consequently more like 

 that of the human subject. The squamous 

 portions of the temporal bone extend over a 

 smaller portion of the sides of the cranium 

 than in man, and their superior margin, instead 

 of forming a convex curve, is almost a straight 

 line. The mastoid processes are represented 

 on either side by a mere ridge of bone, anil 

 the styloid processes by small tubercles. The 

 condyloid processes of the occipital bone are 

 proportionally smaller than in the human sub- 

 ject. The foramen magnum is situated in the 

 middle of the posterior third of the basis 

 cranii, and its plane is inclined upwards from 

 the anterior margin at an angle of 5 from the 

 plane of the basilar process; there are no 

 posterior condyloid foramina but the anterior 

 condyloid foramina, the foramina jugularia, 

 stylo-mastoidea, carotica, spinosa, and ovalia, 

 are in nearly the same relative position as in 

 man ; the principal difference is in the greater 

 distance between the foramen caroticnm and 



the foramen ovale, in consequence of the 

 greater antero-posterior extent of the petrous 

 bone. 



In consequence of the proximity of the 

 foramen magnum to the posterior margin of 

 the skull, a considerable extent intervenes 

 between it and the posterior margin of the 

 bony palate ; this is occupied by the large 

 development of the petrous bones, and a 

 corresponding extent of the basilar element of 

 the occipital. The antero-posterior diameter 

 of the bony palate, in like manner, greatly 

 exceeds that of the corresponding part of the 

 human skull. The zygomatic arches are op- 

 posite the middle third of the skull, as seen 

 from below, while in the human cranium they 

 are included in the anterior moiety. 



The form of the basis cranii differs generally 

 from the bimanous, and manifests the quadru- 

 manous type, in its greater length, in its flat- 

 ness, in the small extent of the receptacle for 

 the brain behind the foramen magnum, in its 

 contraction between the zygomata, and in the 

 large size, and especially the anterior develop- 

 ment, of the bony palate. 



A character, by which the Chimpanzee ap- 

 proximates more closely than the Orang to 

 the human subject, is presented by the nasal 

 bone, which projects, in a slightly arched 

 form, beyond the interorbital plane, while a 

 trace of its original separation into two lateral 

 elements remains at the lower margin of the 

 consolidated and single bone. 



The ascending or nasal portion of the su- 

 perior maxillary bone, which is of greater 

 proportionate size than in the human subject, 

 does not ascend vertically to the orbits, as in 

 man and some of the lower Quadrumana, but 

 slopes backwards, as in the Cynocephali and in 

 the carnivorous mammalia, but in a less degree. 

 The contour of the upper jaw, from the nasal 

 aperture to the incisor teeth, is almost straight, 

 while in the Orang it is rendered concave by 

 the greater development of the intermaxillary 

 bones in the anterior direction. These bones 

 are anchylosed to the maxillary bones in the 

 adults of both the Chimpanzee and Orang ; but 

 in the Chimpanzee the anchylosis takes place 

 at a much earlier period. In the same manner 

 as in man the original separation remains 

 visible, in the palate external to the foramina 

 incmva. The lower jaw, like the upper, is 

 equally characterised by its strength and size 

 in relation to the entire skull ; the symphysis 

 or chin recedes ; but the depth of the jaw in 

 front is less than in the Orang-oetan. The 

 ramus of the jaw forms a more open angle 

 with the body than in the Orang-aetan, and 

 thus more nearly resembles the human struc- 

 ture. The dental formula of the Chimpanzee 

 is as I stated before. The teeth approximate 

 in their proportionate size much more nearly 

 than those of the Orang-oetan to the human 

 teeth, but they differ by the absence of un- 

 broken proximity. A well-marked interval 

 separates the upper laniaries from the con- 

 tiguous incisors, and the lower laniaries are 

 removed by a smaller interval from the con- 

 tiguous bicuspides ; these intervals admit the 



