170 



THE GENERAL ANATOMY OF GORILLA 



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general aspect is quite distinct from the oval contour which characterizes the 

 orbit in Simia. In this respect the Chimpanzee agrees with the Gorilla. 

 The external angular processes of the frontal bone are massive and project 

 strongly, and this also contributes to the square-cut appearance of this part 

 of the face (Fig. 111). 



The outer margins of the orbits are indistinct and bevelled. 



The lachrymal bone is reduced as in Man and though abnormal cases of 

 a well-developed lachrymal hamulus occur, yet in general this process is even 

 more vestigial than in the human skull. The lachrynio-ethmoidal suture is 

 usually replaced (65 - 4% as against 34*6% of lachrynio-ethmoidal sutures in 

 a series of 26 males) by a fronto-maxillary suture which may indeed be of 

 considerable length (10 mm.): the os planum of the ethmoid is reduced con- 

 siderably in vertical extent and is particularly attenuated anteriorly. The 

 number of infra-orbital foramina is variable, but the cases in which a single 

 foramen occurs are just in excess of the other varieties. 



Figs. Ill, 112. Crania of Gorilla and Simia; the former is distinguished by the 

 massive brow-ridges which are continuous from one orbit to the other. 



The nasal bones (Figs. 113, 114, 115) are very characteristic in form, and 

 are conjoined at an early epoch. The combined bones form a single clement 

 of the following shape. From a pointed apex on the level of the supra- 

 orbital ridge, the margins diverge for about 10 mm. (at the level of the 

 junction of the upper and middle thirds of the orbit) ; below this they 

 approach one another again, and here a sharp crest projects from the middle 

 line. Then the margins diverge strongly and the crest is lost at the same time. 

 Finally the lateral margins for the last time converge, but only slightly. 

 The nasal bones thus extend well below the level of the orbits, and their 

 shape distinguishes the bones in the Gorilla equally from those of the Chim- 

 panzee 1 and the Orang-utan. (Cf. Fig. 113 A, B, C.) 



The lateral margins of the apertura piriformis nasi are seen to be formed 

 by the premaxillae which extend up even along the sides of the nasal bone. 



1 A male Chimpanzee skull in the Cambridge Collection presents a remarkable 

 instance of the anomalous occurrence of nasal bones of the type here described as 

 distinctive of the Gorilla. 



