404 PROFESSOR OWEN ON THE OSTEOLOGY OF 



§ 6. Comparison of the Skull of the male Troglodytes Gorilla with that of a male Negro. 



In the side view the most remarkable difference is the small proportional size of the 

 cranium, as defined by the supraorbital ridge and the zygomatic arch from the facial 

 part of the skull, in the Chimpanzee ; notwithstanding the presence of the strong sagittal 

 and lambdoidal cristse which are superadded to the cranial part of the skull, and prolong 

 its extent upwards and backwards beyond the proper walls of the brain-case in the great 

 Ape. 



The temporal ridge, arching upwards and backwards, and blending with its fellow to 

 form the parietal crest, defines the upper contour of the cranium in the Chimpanzee, 

 the intercepted part of the frontal sinking below the converging ridges and forming a 

 concavity in their interspace. In Man the frontal swells out into a broad convexity 

 between those ridges, which are feebly defined by the slight subsidence of the muscular 

 temporal surface below the level of the rest of the frontal, and this indication of a ridge 

 usually disappears before it reaches the coronal suture, where nearly the whole upper 

 surface of the cranial dome intervenes between such indications. 



The rudiment of the lambdoidal ridge in Man curves with the convexity upwards 

 below the suture to terminate in the occipital spine or tubercle, a free tract of bone 

 more than an inch in breadth dividing the lambdoidal from the temporal ridges, and 

 being continued between them upon the mastoid process. In the Chimpanzee the 

 enormous lambdoidal crest, blended with the back part of the temporal ridge, curves 

 with the concavity upwards, as it extends from the mastoid, obliterating the suture, to 

 join the hind end of the sagittal crest ; and the lambdoidal crest terminates the contour 

 of the cranium behind as the sagittal does above. 



In Man the parietal dome rises high above and the occiput swells out below the 

 rudimentary lambdoidal ridge, whilst the larger and longer mastoid process, projecting 

 downwards and extended forwards beneath the meatus auditorius externus, supports 

 the vaginal plate of the tympanic or auditory process ; but in the Chimpanzee the 

 tympanic or auditory process, presenting the form of a semicylindrical tube, is wholly 

 in advance of the shorter mastoid process, and has no vaginal process at its outer end. 

 The post-glenoid process of the squamosal (middle root of the zygoma) is relatively 

 thicker and longer, but more obtuse in the Chimpanzee. 



The zygoma is not only much stronger, but the squamosal and malar portions have 

 different forms and proportions in the Chimpanzee ; the squamosal is as deep and as 

 long as the malar part, instead of being shallower and longer as in Man ; and its upper 

 border rises in the Chimpanzee into an angular form. The malar portion is accordingly 

 longer, and does not decrease in depth after leaving the body of the bone as in Man. 

 The posterior border of the frontal process of the malar is slightly concave or nearly 

 straight in the Chimpanzee ; it forms a strong sigmoid curve in Man, convex backwards 

 at its upper half. The supraorbital ridge projects very slightly beyond the slope of the 



