THE CHIMPANZEES AND ORANGS. 81 
Gorilla. The upper boundary of the nasal cavity, formed by the cribriform plate of the 
zethmoid and the nasal bones, is on a level with the middle of the orbit in the Papuan, 
but with the floor of the orbit in the Gorilla. The extent, therefore, of solid interorbital 
median wall is much greater in the Gorilla, and forms a striking differential feature 
with Man, as seen in the vertical section (Pls. XXVIII. and XXX.). 
Sinuses extend from the middle meatus upwards on each side this septum into the 
interorbital space, as high as the base of the middle fourth of the superorbital ridge (f), 
where they answer to the ‘frontal sinuses’ of Man; but, owing to the peculiar deve- 
lopment of that ridge in the Gorilla, they occupy no part that can properly be 
called forehead in that animal. The superorbital ridge itself is chiefly composed 
of solid bone with a small extent of minute cancellous structure in the middle of the 
substance. 
The inner or vitreous table of the calvarium is better defined, where it is defined, in the 
Gorilla than in Man, as is shown in the section (Pl. XXVIIL.) for about an inch above 
the foramen magnum, at the base of the lambdoidal crest, and along the posterior half 
of the base of the sagittal crest ; elsewhere it blends with the outer table to form a dense 
compact roof of bone. The whole of the enormous sagittal crest (11, 3) is formed of 
bony substance almost as compact. ‘The basal half of the lambdoidal crest (3,1), exposed 
by the section, is cancellous at its middle ; and the boundary line between this and the 
sagittal crest is well marked by the long venous canal continued downwards from the 
foramen parietale (3). 
It is scarcely necessary to say that the parietal and lambdoidal cristee, which in the 
Gorilla surpass in height those of all the Carnivora, do not exist, even rudimentally, in 
any of the races of Mankind. The crucial ridge in Man is developed from a lower part 
of the superoccipital than is the lambdoidal ridge of the Anthropoid apes. 
If we next proceed to compare the nasal chamber itself in the skulls of the Gorilla 
and Papuan, we have first to notice the greater proportional length of that cavity in the 
Gorilla, especially in the extent of its bony floor (20-22), but the turbinal plates have 
not a corresponding antero-posterior extent. ‘The premaxillary is relatively longer and 
larger, and the part below the nostril, divided by the section at 22, Pl. XXVIII., slopes 
more forwards than in the Papuan. The answerable part (22, Pl. XXX.), though 
confluent with the maxillary in Man, is well defined by the incisive canal: this is 
divided at its nasal end in the Gorilla, as in some Papuan and other Human skulls, 
by the junction of a process of the premaxillary with the fore part of the nasal spine of 
the maxillary (21). 
The remains of the premaxillary suture, which are obvious in the Gorilla for half an 
inch upon the under surface of the palate, may be traced for an inch upwards and 
backwards along the lateral wall of the incisive canal into the nasal cavity, where it is 
lost, but appears again at the upper and lateral part near the nostril (Pl. XXVIII. 22"), 
