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poid apes do.' This inference has been fully borne out by the rest 

 of the skeleton of the gorilla, subsequently acquired. 



In the chimpanzee, as in the orangs, gibbons, and inferior 

 Simice, the lower surface of the long tympanic or auditory process 

 is more or less flat and smooth, developing in the chimpanzee 

 only a slight tubercle, anterior to the stylohyal pit. In the gorilla 

 the auditory process is more or less convex below, and developes a 

 ridge, answering to the vaginal process, on the outer side of the 

 carotid canal. The processes posterior and internal to the gleiioid 

 articular surface, are better developed, especially the internal one, 

 in the gorilla than in the chimpanzee; the ridge which extends 

 from the ectopterygoid along the inner border of the foramen ovale, 

 terminates in the gorilla by an angle or process answering to that 

 called 'styliform' or l spinous' in man, but of which there is no 

 trace in the chimpanzee, orang, or gibbon. 



The orbits have a full oval form in the orang; they are almost 

 circular in the chimpanzee and sianiang; more nearly circular, 

 and with a more prominent rim in the smaller gibbons; in the 

 gorilla alone do they present the form which used to be deemed 

 peculiar to man. There is not much physiological significance in 

 some of the latter characters; but, on that very account, I 

 deem them more instructive and guiding in the actual com- 

 parison. The occipital foramen is nearer the back part of the 

 cranium, and its plane is more sloping, less horizontal, in the 

 siamang, than in the chimpanzee and gorilla. Considering the less 

 relative prominence of the fore part of the jaws in the siamang, as 

 compared with the chimpanzee, the occipital character of that 

 gibbon and of other species of Hylobates indicates well their 

 inferior position in the quadrunianous scale. 



In the greater relative size of the molars, compared with the 

 incisors, the gorilla makes an 'important closer step towards man 

 than does the chimpanzee. The molar teeth are relatively so 

 small in the siamang, that notwithstanding the small size of the 

 incisors, the proportion of those teeth to the molars is only the 

 same as in the gorilla : in other gibbons (Hylobates lar\ the four 

 lower incisors occupy an extent equal to that of the first four 

 molars, in the chimpanzee equal to that of the first three molars, 

 in the sianiang equal to that of the first two molars and rather 

 more than half of the third, in man equal to the first two molars 

 and half of the third : in this comparison the term molar is applied 

 to the bicuspids. 



G2 



