SKELETON OF QUADRUMANA 



537 



in Tr. Gorilla as in Tr. niger^ but less completely, a linear indi- 

 cation of the median suture remaining along the exterior surface : 

 the coalesced upper portions of the nasals ascend higher above 

 the nasal processes of the maxillary than in Tr. niger, become 

 contracted between those processes and there project slightly, 

 their median coalesced margins being produced forward : they 

 expand at their lower halves, and articulate not only with the 

 maxillaries, 21, but with an expanded superior portion or dis- 

 memberment of the premaxillaries, 22. In the immature Tr. 

 niger, the maxillo-premaxillary sutures show that each pre- 

 maxillary bone terminates above in a point which does not 

 reach the nasals. The orbits have 

 a more subquadrate form, with the 



358 



.^ 



Gorilla, cm 



angles rounded oiF, in Tr, Gorilla 

 than in Tr. niger ; but their peri- 

 phery is less sharply defined, espe- 

 cially below, than in Tr. niger. The 

 ethmoidal cells are more swollen 

 out, giving the interorbital space 

 a greater breadth below and the 

 lachrymal fossae a more anterior 

 aspect in Tr. Gorilla. The infra- 

 orbital canal issues upon the face 

 relatively lower and further from the 

 orbit. The whole nasal bone is rela- 

 tively longer, and the distance from 

 the orbits to the external nostril greater in the Tr. Gorilla. 

 The malar bone, 26, is more convex outwardly, and is more remark- 

 able for its vertical extent : it is flatter and developed more trans- 

 versely in the Tr. niger. The larger proportional size of the 

 canines in Tr. Gorilla impresses a corresjoonding difference upon 

 the alveolar part of the maxillary bone in that species. Fig. 357 

 contrasts the broad flattened superoccipital surface of the Gorilla 

 mth the convexity of the same part in the Tr. niger, fig. 'd5Q> : the 

 difference is due to the much thicker and broader lambdoidal 

 ridge in the larger species, which prolongs the surface beyond the 

 cerebellar fossa, and gives the condyles and foramen magnum a 

 rather more advanced position as compared with the Tr. niger. 

 The next character, ex[)licable in relation to the greater weight of 

 the skull to be poised upon the atlas, is the greater prominence of 

 the mastoid processes in the Tr. Gorilla, which are represented 

 by only a rough ridge in the Tr. niger. These protuberances are 

 cellular, and with a very thin outer layer of bone in the Tr. 

 Gorilla. The lower surface of the long tympanic or auditory 



