22 Professor Owen, [Feb. 4, 



prominences in the naso-facial part of the skull ; but they do not 

 really affect the question as between the gorilla and chimpanzee. All 

 naturalists know tliat the semnopitheques of Borneo have long noses ; 

 but the proboscidiform appendage which gives so ludicrous a mask to 

 those monkeys is scarcely the homologue of the human nose, and is 

 unaccompanied by any such modification of the nose-bones as gives the 

 true anthropoid character to the human skull, and to which only the 

 gorilla, in the ape tribe, makes any approximation. 



No orang, chimpanzee, or gibbon shows any rudiment of mastoid 

 processes ; but they are present in the gorilla, smaller indeed than in 

 man, but unmistakeable ; they are, as in man, cellular, and with a thin 

 outer plate of bone. This fact led the lecturer to express, when in 

 respect to the gorilla, only the skull had reached him, the following 

 inference, viz. : " from the nearer approach which the gorilla makes to 

 man in comparison with the chimpanzee, or orang, in regard to the 

 mastoid processes, that it assumed more nearly and more habitually 

 the upright attitude than those inferior anthropoid 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. Tlie 

 processes posterior and internal to the glenoid 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 " 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 siamang ; 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, the lecturer deemed 

 them more instructive and guiding in the actual comparison. 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 Hijlobates 

 indicates well their inferior position in the quadrumanous 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 



