35 



succession takes place precisely as in the human subject, but the per- 

 manent teeth, and especially the incisors and canines, are proportion- 

 ally longer. The particulars of their form and arrangement are 

 given at length. 



This portion of the paper was accompanied by an extensive series 

 of admeasurements of the different parts of the skeleton in the adult 

 and young Chimpanzee, compared with those of the young and adult 

 Orang; and was further illustrated by numerous drawings, and by 

 the exhibition of Mr. Walker's skeleton of the Chimpanzee, lent by 

 him for the purpose. 



The second portion of the paper commences with the remark 

 that the opportunity which the rare and interesting skeleton of the 

 adult Chimpanzee, in the possession of Mr. Walker, had afforded of 

 tracing the changes of structure occurring in that Ape, in its progress 

 to the adult condition, had induced the author to review the question 

 relative to the identity of the young Simia Sattjrus with the great 

 Pongo of Borneo, formerly brought by him under the notice of the 

 Society ('Proceedings of Committee of Science and Correspondence,' 

 Part I. p. 9); and to consider the osteological structure of the latter, 

 or adult Orang, with reference to that of its less powerful and 

 more anthropoid congener, the Chimpanzee. This comparison 

 would show that the number and value of the points of resem- 

 blance, or of approximation, to the Bimanous structure are in 

 favour of the Chimpanzee ; although in this, as in most other in- 

 stances, there are some particulars of its organization indicative of 

 a more marked relation with the inferior forms of the group than 

 with those which rank immediately below it. 



In common with the skull of the Mandrill that of the adult Orang 

 is remarkable for its flattened occiput, formidable canine teeth, huge 

 jaws, widely expanded zygomatic arches, and strongly developed 

 cranial ridges ; but it exhibits a marked distinction in its less brutalized 

 expression, resulting from the more perpendicular slope of the face, 

 the absence of the projecting supraciliary ridges, the greater expan- 

 sion of the cerebral cavity, and the non-development of the supra- 

 maxillary ridges. Its cranium is less flattened at the vertex than that 

 of the Chimpanzee; and but little exceeds in capacity that of the young 

 at the period of acquiring its first permanent molares, the increase 

 in size being chiefly dependent on the thickening of the walls of the 

 skull. The ridges which circumscribe on the frontal bone the origin 

 of the temporal muscles inclose a triangular space, the smoothness 

 of which strongly contrasts with the irregular surface of the re- 

 mainder of the cranium ; and the interparietal crest rises, as in 

 the Hycena and other Carnivora, high above the general level. The 

 situation of these ridges, with reference to the sutures, is only de- 

 terminable by comparing the faint commencement of their growth 

 in the young animal, very few traces of the sutures remaining in the 

 adult skull. That between the ala of the sphenoid bone and the 

 descending angle of the parietal, by means of which the frontal 

 and temporal are kept separate, and which offers one of the few 

 osteological differences in which the Orang has a closer approxima- 



