1859.] on the Gorilla, 23 



those teeth to the molars is only the same as in the gorilla : in other 

 gibbons {Hylobates lar)^ the four lower incisors occupy an extent 

 equal to that of the first four molars, in the chimpanzee equal to that 

 of the first three molars, in the siamang equal to that of the first two 

 molars and rather more than half of the third, in man equal to the 

 first two molars and half of the third : in this comparison the term 

 molar is applied to the bicuspids. 



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-lOths, in the chim- 

 panzee 6-lOths, in the siamang it is only 4-lOths. 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 simiae 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 simiae than the gorilla does, and in a marked 

 degree. 



Every legitimate deduction from a comparison of cranial characters 

 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 

 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 {Eopilhecus) 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 



(q _ O q ^ Ov 



P— -—» OT— ^ ) 

 3 — 3 3 - o/ 



to 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, 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 humerus 

 of a quadrumanous animal i^Dryopithecus)^ equalling the size of those 



