791 



angular in the Gorilla ; its upper border, which does not rise higher than opposite the 

 middle of the orbit, being almost straight ; the continuation of the line of this border by the 

 mastoid makes the squamosal appear much longer from before backwards than this temporal 

 element really is. In Man the mastoidal element developes no continuation of the squamous 

 plate, but the hind border of this plate curves down to the place of the primitive suture be- 

 tween the squamosal and mastoid. The whole of the squamosal receives air-cells from the 

 mastoid in the Gorilla, and its exterior surface is made convex and, as it were, swollen out 

 by them : no part of the squamosal is so modified in Man. 



At the first view of the skull of the great Gorilla, one is struck by its superior size to the 

 human skull, especially its greater length, and the greater breadth of the face and of the oc- 

 ciput : the brain-case is made to appear more contracted in proportion than it actually is, by 

 the superaddition of the enormous intermuscular crests and superorbital ridge : it would 

 seem, indeed, as if the osseous matter required to form the expanded cerebral chamber in 

 the human skull had been here expended in the formation of the great external produc- 

 tions. Notwithstanding, however, this superiority of size in certain dimensions, and the 

 apparently massive character of the skull of the Gorilla, it is actually lighter than that of 

 Man. The cranium of the adult male Troglodytes Gorilla, here described, weighed 1 Ib. 7 oz. 

 8 drs. avoirdupois, whilst the cranium of a male Australian, without the lower jaw, weighed 

 1 Ib. 8 oz. 10 drs. This unexpected result is due to the greater size and extent of the air-cells 

 in the Troglodytes Gorilla. The air introduced from the tympanic chamber into the mastoid 

 extends backwards into cells, continued along the base of the lambdoidal crista to its junction 

 with the parietal crista, and from the mastoid forwards, inflating the whole squamosal plate 

 as far as the alisphenoid, which, with the pterygoids, receives air from the sphenoidal 

 sinuses. 



The frontal sinuses are divided from each other by a strong median vertical septum, and 

 extend far outwards along the base of the superorbital crest, but do not rise into the cranial 

 plate of the frontal : they open below into the middle meatus, as in Man. The great maxil- 

 lary sinus or antrum is chiefly remarkable for its extension upwards, where it swells out the 

 maxillary contribution to the inner wall of the orbit ; the nasal aperture of the antrum, of a 

 rounded form and two-thirds of an inch in diameter, is covered by the overhanging inferior 

 turbinal bone : the lacrymal canal terminates at the upper part of the orifice of the antrum, 

 not in advance of it, as in Man. 



The osseous parts of the olfactory capsule, which have coalesced with the prefrontals and 

 form the ' superior ' and ' middle ' turbinal processes of the aethmoid, are present, as well as 

 the large independent inferior turbinals : these are all longer in proportion than in Man. 



The chief differences which the cranium and teeth of the Troglodytes Gorilla present as 

 compared with those parts of the Human structure may be summed up as follows : 



1. The smaller proportional size of the cranium. 



2. The more backward position of the foramen magnum, and its more oblique plane in re- 

 lation to that of the base of the skull. 



3. The smaller relative size and more backward position of the occipital condyles. 



4. The longer basioccipital, and broader, flatter and lower superoccipital. 



5. The longer basisphenoid and shorter alisphenoids. 



