398 PROFESSOR OWEN ON THE OSTEOLOGY OF 



Tr. Gorilla as in that sex of the Tr. niger, the incisors are proportionally to those in 

 TV. niger as much smaller, and the molars as much larger, as in the male Tr. Gorilla. 

 The last molar not only shows the same equality of size as in the male Tr. Gorilla, but 

 in the skull of the female here described presents a greater complexity of the crown by 

 the outer and posterior lobe being notched, so that the outer half of the wisdom-tooth 

 is here trilobate. 



The infraorbital canal is short, wide and shallow, the foramen lacerum anterius sub- 

 quadrate, and the olfactory fossa as deep and well-defined in the female as in the 

 male Tr. Gorilla. In short, all the distinctive characters of the species afforded by the 

 disposition of sutures, forms of foramina, and proportions of bones and teeth, are as 

 well-marked in the comparison of the skulls of the females of the two species as in that 

 of the males : in such modifiable characters as the bony ridges dependent upon mus- 

 cular development we find a more marked distinction in the female Tr. Gorilla, as com- 

 pared with the female Tr. niger, in the presence of a ridge, the parietal one, e. g., which 

 does not exist in the female of the smaller species of Chimpanzee at any age. 



Even in the female Tr. Gorilla, in which the apices of the tubercles of the teeth are 

 but shghtly abraded, the temporal ridges have met along the whole line of the sagittal 

 suture, where a narrow groove indicates their original distinction. In one old male of 

 the Tr. Gorilla the temporal ridges, though confluent along their bases, diverge as they 

 rise and form two parallel parietal cristse, divided by a deep angular channel. Amongst 

 other varieties noticeable in the series of skulls of this remarkable species, I may mention 

 the existence of a venous foramen in each squamosal of the female skull, situated about 

 ten lines above the meatus auditorius : the infraorbital foramen is double on one side 

 and single on the other in two of the skulls. 



With regard to varieties in the skulls of the adult TV. niger, I have seen in one old 

 male three anterior condyloid foramina on each side instead of the normal single fora- 

 men ; and in the same skull the middle of the basioccipital was perforated from above 

 obliquely downwards and forwards by a canal, probably venous, of two lines iu 

 diameter. 



On a review of the differences pointed out in the preceding comparisons, the stronger 

 zygomatic arches, with the more developed sagittal and lambdoidal crests, might be 

 viewed as adaptive developments concomitant on the presence of larger canines, and 

 indicative of a larger and more powerful variety of Chimpanzee ; but the larger propor- 

 tional molars and the smaller proportional incisors, the more equal and complex ultimate 

 molar tooth, together with the prominence — slight as it is — of the nasal bones at their 

 median line of coalescence, and above all, the reappearance of thepremaxillaries upon the 

 face above the nostril with their longer enduring sutures, constitute a series of differential 

 characters of more importance than such as are due to greater bulk or activity of 

 muscles, and not to be explained by the operation of external circumstances favouring 

 greater general development of size and power. These characters, also, repeated in 



