390 



QUADRUMANA, 



has taken place during the transition of the animal from adolescence to 

 maturity. 264 



The skull of the Orang, in three stages, from infancy to maturity, exhibiting the gradual development of 

 the facial outline, and progressive change in the form of the cerebral portion. 



The skull of the young Orang has a considerable resemblance to 

 that of the human subject. Not only does the volume of the cranium 

 preponderate over that of the face, but it is dignified with a tolerable 

 forehead. The jaws are comparatively moderate, and the teeth (deci- 

 duous) are small. The cranium is smooth, and regularly convex. But, 

 as maturity advances, and during the process of the second dentition, 

 the face becomes developed and protruded, the jaws expand, the lower 

 increasing amazingly in breadth, and the zygomatic arch alters in form, 

 and becomes stouter. The persistent teeth are large and strong, the 

 incisors are enormously thick, and the canines are of vast strength and 

 magnitude, constituting most formidable weapons. This development of 

 the face tends to throw back the forehead, and the more so, as the 

 cavity of the cranium, instead of enlarging in a commensurate ratio, 

 scarcely increases at all after the acquisition of the first permanent 

 molars ; but its walls become thicker, and a bold ridge, commencing at 

 each external angular process of the temporal bone (or at the outside of 

 each orbit), passes obliquely upward, enclosing a smooth triangular por- 

 tion of the frontal bone : on the posterior margin of the frontal bone these 

 ridges, which, until complete maturity, do not coalesce, but remain sepa- 

 rate throughout all their extent, ultimately meet, and form an elevated 

 interparietal crest, as in carnivorous animals, betokening the vast 

 extent and power of the temporal muscles that act on the lower jaw. At 



