789 



considerably greater in the Gorilla than in Man. The stylomastoid foramen is exterior to the 

 stylohyal fossa, not directly behind it as in Man, in whom the stylohyal bone becomes anchy- 

 losed at maturity with that fossa and forms the so-called ' styloid process of the temporal.' 

 This process is wanting in the Gorilla, and there is but a rudiment of the vaginal process. 



The tympanic, which anchyloses with the mastoid, squamosal and petrosal as in Man, is of 

 greater length than in Man : it forms no part of the glenoid fossa, which is divided from it 

 by the postglenoid process, and the rudiment of the ' fissura Glaseri ' is quite behind the 

 glenoid fossa in the Gorilla, whilst in Man, from the different relative position and shape of 

 the tympanic or auditory process, the ' fissura Glaseri ' is described as dividing the glenoid 

 fossa transversely. The inner termination of the meatus auditorius is very obliquely cut off, 

 but in a different direction from that in Man : in him it is from behind inwards and for- 

 wards, the anterior wall of the meatus being longer than the posterior one : in the Gorilla the 

 inner end of the meatus is cut off obliquely from above inwards, downwards and forwards : at 

 the beginning of the meatus its vertical diameter is greatest, but as it penetrates the cranium 

 the transverse diameter becomes greater, the depth decreasing, and it rather suddenly expands 

 at its inner very oblique termination. The superior size of the mastoid processes in Man relates 

 to the greater amount of muscular action required for the support and movements of the skull, 

 which is balanced upon the erect vertebrae of the trunk : in the Quadrumana, where the skull 

 is thrown more forwards, its support is derived more from the action of the great nuchal 

 muscles inserted into the occiput than from that of the sternomastoids ; but we may infer, 

 from the nearer approach which the Troglodytes Gorilla makes to Man, in comparison with 

 the Troglodytes niger, or with the known species of Orang (Pithecwi), in regard to its 

 mastoid processes, that it assumed more nearly and more frequently the upright attitude than 

 the inferior anthropoid Apes do. 



The air-cells from the tympanum, which are confined to the mastoid in Man, extend in 

 the Gorilla into the squamosal, inflating it above the base of the zygomatic process, and as 

 far forwards as its junction with the frontal, where the squamosal sinuses are contiguous to, 

 though they seem not to communicate with, those of the alisphenoid. 



The petrosal is larger in the Gorilla than in Man ; its antero-posterior diameter especially 

 is greater : its eustachian process is much more developed and more distinct from the proper 

 apex of the petrosal, which is less jagged than in Man, and rests more completely upon the 

 base of the alisphenoid, almost filling up the vacuity called in Man ' foramen lacerum medius.' 

 The carotid foramen is smaller than in Man : the prejugular process from the inner side of 

 the foramen caroticum abuts upon a corresponding process of the basioccipital, and with it 

 forms the anterior boundary of the foramen jugulare. 



The chief characteristics of the frontal, due to its smaller size and the superorbital ridge, 

 have already been noticed : besides these deviations from the Human type, the ectorbital pro- 

 cesses stand further out before they bend down to join the malar, and the postorbital angles 

 descend much lower into the temporal fossa and form a longer wedge between the alisphenoid 

 and malar bones, the point terminating on a level with the floor of the orbit. The vomer is 

 deeper and more oblique than in Man, and does not reach so far forwards. The coalesced 

 prefrontals {lamina medics aetkmoidei) are connate, as in Man, with the olfactory capsules 

 forming the ethmoidal cells, the superior turbinals, the ' partes planae ' and the cribriform 



