84 



The proportion of the ascending ramus to the length of the 

 lower jaw tests the relative affinity of the tailless apes to man. 



In a profile of the lower jaw, compare the line drawn vertically 

 from the top of the coronoid process to the horizontal length along 

 the alveoli. In man and the gorilla it is about 7-10ths, in the 

 chimpanzee 6-10ths, in the siamang it is only 4-10ths. The 

 siamang further differs in the shape and production of the angle of 

 the jaw, and in the shape of the coronoid process, approaching the 

 lower simise in both these characters. In the size of the post- 

 glenoid process, in the shape of the glenoid cavity which is almost 

 flat, in the proportional 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 simise than 

 the gorilla does, and in a marked degree. 



Every legitimate deduction from a comparison of cranial cha- 

 racters makes the tailless Quadrumana recede from the human 

 type in the following order, gorilla, chimpanzee, orangs, gibbons; 

 and the last-named in a greater and more decided degree. 



Those 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 So- 

 ciety 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, 4 feet in height, discovered in 1839 

 by Dr Lund in a limestone cavern in Brazil was shewn by its 



/ 3 3 3 3\ 



molar dentition ( p - - , m - ^ ) to belong to the platyrrhine 

 \ o o o o/ 



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, is so closely allied to the gibbons as to scarcely 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 



