SKELETON OF QUADRUMANA. 535 



prominent process ; the tympanic air-cells are continued therefrom 

 into the squamosal. The interorbital sinuses do not ascend to 

 within half an inch of the upper level of the orbits, and there is 

 consequently no proper frontal sinus : a cancellous structure occu- 

 pies the usual place of this, beloAv which the part of the interorbital 

 septum formed by the hinder crista of the nasal bone and the 

 frontal presents a very compact dense structure. The small venous 

 canal continued from the foramen c^cum traverses the base of this 

 septum to terminate at the lower end of the short nasal bone. 

 The ' lamina perpendicularis tethmoidei,' or coalesced prefrontals, 

 presents a quadrate form. The floor of the nasal cavity is long 

 and thick, as compared with that in Man, and a larger proportion 

 of it is contributed by the premaxillary. The orbits are directed 

 forward and have a full oval shape. The area of the nasal cavity 

 equals more than one third of that of the cranial cavity. The 

 most anterior part of this cavity is formed by the deep, narrow, 

 and well-defined rliinencephalic fossa : the ^ crista galli ' is rudi- 

 mental. The division of the prosencephalic compartment, for the 

 anterior and middle lobes of the cerebrum, is very slightly 

 defined by the orbitosphenoid. The tentorial ridge is not con- 

 tinued backward beyond the petrosal. The nasal end of the 

 incisive canal is divided by the process extending from the pre- 

 maxillary to the maxillary ; but this is the only part of the pre- 

 maxillary which does not coalesce with the maxillary. The 

 turbinal plates are less developed than in the Gorilla ; the lower 

 one is shorter than the one above ; and there is not any plate 

 answering to the small superior turbinal in the Gorilla and in 

 Man. There is, in some Orangs' skulls, a process, formed by the 

 anchylosed base of the stylo- 

 hyal, which is defended in 

 front by a low and obtuse 

 vaginal process. The com- 

 pact wall of the mandibular 

 symphysis is thick and dense. 

 The symphysis slopes from 

 above downward and back- 

 Avard. 



In the genus Troglodytes, 

 the squamosal, fio-. 356, 27, ^, . ^ , 



-■■ . , *^ . , Cbiinpaiizee {Troglodytes niger, male), cm-. 



usually articulates with the 



frontal, 11 ; the premaxillaries coalesce with the maxillaries earlier 

 than in Pithecus, the alveolar part of the suture being obliterated 

 before the nasal portion ; the palatal part long remains. In the 



