260 PROFESSOR OWEN ON THE EXTERNAL CHARACTERS 
third, in Man equal to the first two molars and half of the third: in this comparison 
the term ‘molar’ is extended to the bicuspids. 
The proportion of the ascending ramus to the length of the lower jaw tests the rela- 
tive affinity of the tailless Apes to Man. 
In a profile of the lower jaw, I 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 45ths, in the Chimpanzee ;sths, in the Siamang it is only 7‘oths of the length 
of the jaw. 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 Simie@ 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 Simie, than the Gorilla does, and in a marked 
degree. 
’ Every legitimate deduction from a comparison of cranial characters makes the tail- 
less Quadrumana recede from the Human type in the following order :—Gorilla, Chim- 
panzee, Orang, Gibbons ; and the last-named in a greater and more decided degree. 
These comparisons have of late been invested with additional interest from the dis- 
coveries of remains of quadrumanous species in different members of the tertiary for- 
mations. 
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 
(probably miocene) tertiaries, to the Indian genus Semnopithecus. 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 ina 
limestone-cavern in Brazil was shown by its molar dentition (p.=, m.=*) 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’, are so closely allied to the Gibbons, as scarcely 
to justify the generic separation which has been made for it under the name Plio- 
pithecus. 
The fossil femur from the miocene of Eppelsheim, recognized as quadrumanous by 
Professor Kaup, proves, upon comparison, to be most like the femur in the Gibbons °. 
The quadrumanous fossils from the miocene beds of Pikermi are referred by Wagner 
to a genus Mesopithecus, more allied to Semnopithecus than to Hylobates*. 
' Owen’s ‘ British Fossil Mammals and Birds,’ p. xlvi. figs. 1-4. 
* © Ostéographie,’ fase. iv., ‘‘ Primates Fossiles,”’ p. 54. * Trans. Zool. Soc. vol. y. pt. i. p. 18. 
* «Die fossilen Knochen-Ueberreste von Pikermi,” 4to, 1854. 
The lower molar teeth from the eocene sand at Kyson, Suffolk, which at the time of their discovery most 
