THE CHIMPANZEE AND ORANG UTAN. 377 
d,e. The two bicuspides. 
f. The first true molar, its fangs yet imperfect. 
g. The second molar. 
On the right hand, a front view is given of the first and second permanent incisors, as 
they appear partly worn down in the adult. 
PLATE LII. 
The base of the skull of the adult Chimpanzee, natural size. The rudiments of the per- 
manent teeth, a to g, are figured in a position corresponding to those in the jaws of the 
adult. The formation of the last molar, or dens sapientig, h, had not commenced in 
the young cranium from which the rest of the permanent teeth were taken. 
PLATE LIII. 
Side view of the cranium of an adult Orang Utan. A front view of the first perma- 
nent incisor, d, and the rudiments of the permanent teeth, a to g, from the jaws of a 
young Orang are subjoined, proving its identity with the adult, or supposed Pongo. 
This Plate is taken from a cranium in the possession of Mr. Cross, of the Surrey 
Zoological Gardens, who obligingly sent his specimen to me for the purpose of describing 
and figuring it. On comparing it with the skull of the Pongo, or adult Orang, in the 
Museum of the College of Surgeons, I noted the following differences : 
The skull belonging to Mr. Cross is shorter in the antero-posterior diameter, and rises 
higher at the verter. The supra-orbitary ridges are more prominent ; the plane of the 
orbits is more vertical, and their lateral exceeds their perpendicular diameter. The 
profile line of the skull is concave between the glabella and incisor teeth, while in the 
specimen in the Museum of the College it is almost a straight line between the same 
parts. The symphysis of the jaw, from the interspace of the mesial incisors to the origin 
of the genio-hyoidei muscles, measures 21 inches in Mr. Cross’s specimen, but equals 
34 inches in the Pongo in the College Museum. There is also a remarkable difference 
in the position of the zygomatic suture: in the Pongo of the College Museum it com- 
mences at the distance of a quarter of an inch from the orbital process of the malar bone 
and extends obliquely backwards to within 1+ inch of the origin of the zygomatic pro- 
cess of the temporal bone ; in Mr. Cross’s specimen, the same suture commences 
8 lines from the orbital process of the malar bone and extends to within 10 lines of the 
origin of the temporal zygomatic suture, so that it is much nearer the middle of the 
sygoma. 
With these differences, however, there exist the same form and proportions of the 
teeth, and the same peculiarities of the foramina and sutures which distinguish the 
Orang from the Chimpanzee. So that, although the difference in the shape and general 
