68 



55 to 60 in the Troglodytes niger. The difference in the facial 

 angle between the young and adult apes, (which, in the young 

 chimpanzee, approaches 60 to 65,) depends upon those changes 

 consequent upon the shedding of the deciduous teeth and the con- 

 comitant development of the jaws and intermuscular processes of 

 the cranium. 



But the knowledge of the species of these anthropoid apes has 

 been further increased since the acquisition of a distinct and pre- 

 cise cognisance of the characters of the adults of the orang and 

 chimpanzee. First, in reference to the orangs of Borneo, speci- 

 mens have reached this country which show that there is a smaller 

 species in that island, the Simia Morio, in which the canines are 

 less developed, in which the bony cristce are never raised above 

 the level of the ordinary convexity of the cranium, and in which 

 the callosities upon the cheeks are absent, associated with other 

 characteristics plainly indicating a specific distinction. The Rajah 

 Brooke has confirmed the fact of the existence in the island of 

 Borneo of two distinct species of red orangs j one of a smaller size 

 and somewhat more anthropoid ; and the larger species presenting 

 the baboon-like cranium. 



In reference to the black chimpanzee of Africa also, another 

 very important addition has been, recently, made to our knowledge 

 of those forms of highly developed quadrumana. In 1 847 I received 

 a letter from Dr Savage, a church-missionary ab Gaboon, on the 

 west coast of tropical Africa, enclosing sketches of the crania of an 

 ape, which he described as much larger than the chimpanzee, 

 ferocious in its habits, and dreaded by the negro natives more 

 than they dread the lion or any other wild beast of the forest. 

 These sketches showed plainly one cranial characteristic by which 

 the chimpanzee differs in a marked degree from the orangs; viz. 

 that produced by the prominence of the super-orbital ridge, which 

 is wanting in the adult and immature of the orangs. That ridge 

 was strongly marked in the sketches transmitted. At a later 

 period in the same year, were transmitted to me from Bristol two 

 skulls of the same large species of chimpanzee as that notified in 

 Dr Savage's letter ; they were obtained from the same locality in 

 Africa, and brought clearly to light evidence of the existence in 

 Africa of a second larger and more powerful ape, the Troglodytes 

 gorilla. They are described and figured in the third Volume 

 of the Transactions of the Zoological Society, 1848. 



The additional facts, subsequently ascertained respecting the 



