3^ Zoological Society : — 



in both these characters. In the size of the post-glenoid process, in 

 the sliape of the glenoid cavity which is almost flat, in the propor- 

 tional size of the petrous bone, and in the position of the foramen 

 caroticum, the Siamang departs further from the human type, and 

 approaches nearer that of the tailed SimicBy than the Gorilla does, 

 and in a marked degree. 



Every legitimate deduction from a comparison of cranial charac- 

 ters makes the tailless Quadrumana recede from the human type in 

 the foUoveing order : — Gorilla, Chimpanzee, Orangs, Gibbons, and 

 the last named in a greater and more decided degree. 



These comparisons have of late been invested with additional 

 interest from the discoveries of remains of quadrumanous species in 

 different members of the tertiary formations. 



The first quadrumanous fossil, the discovery of which by Lieuts. 

 Baker and Durand is recorded in the * Journal of the Asiatic 

 Society of Bengal,' for November, 1836, has proved to belong, like 

 subsequently discovered quadrumanous fossils in the Sewalik (pro- 

 bably miocene) tertiaries, to the Indian genus Semnopithecus. The 

 quadrumanous fossils discovered in 1839, in the eocene deposits of 

 Suffolk, belong to a genus (^Eopithecus) having its nearest affinities 

 with Macacus. The monkey's molar tooth from the pliocene beds 

 of Essex is most closely allied to the Macacus sinicus. The remains 

 of the large monkey, four feet in height, discovered in 1839 by 

 Dr. Lund in a limestone cavern in Brazil was shown by its molar 

 dentition (j9^» '^^) ^^ belong to the platyrrhine family now 

 peculiar to South America. The lower jaw and teeth of the small 

 quadrumane discovered by M. Lartet in a miocene bed of the South 

 of France, and described by him and De Blainville, are so closely allied 

 to the Gibbons, as scarcely to justify the generic separation which 

 has been made for it under the name Pliopithecus. 



Finally, a portion of a lower jaw with teeth and the shaft of a 

 humerus of a quadrumanous animal (Dtyopithecus), equalling the size 

 of those bones in Man, have been discovered by M. Fontan, of Saint- 

 Gaudens, in a marly bed of Upper Miocene age, forming the base of 

 the plateau on which that town is built. The molar teeth present 

 the type of grinding surface of those of the Gibbons (Hylobates), 

 and, as in that genus, the second true molar is larger than the first, 

 not of equal size, as in the human subject and Chimpanzee. The 

 premolars have a greater antero-posterior extent, relatively, than in 

 the Chimpanzee, and in this respect agree more with those in the 

 Siamang. The first premolar has the outer cusp raised to double 

 the height of that of the second ; its inner lobe appears from 

 M. Lartet's figure to be less developed than in the Gorilla, certainly 

 less than in the Chimpanzee. The posterior talon of the second 

 premolar is more developed, and consequently the fore and aft extent 

 of the tooth is greater than in the Chimpanzee ; thereby the second 

 premolar of Dryopithecus more resembles that in HylobateSy and 

 departs further from the human type. 



The canine, judging from the figures published by M. Lartet*, 

 * * Comptes Rendus de TAcademie des Sciences.' Paris, vol. xliii. 



