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VIII. Osteological Contributions to the Natural History of the Chimpanzees (Troglodytes) 
and Orangs (Pithecus).—No. V. Comparison of the Lower Jaw and Vertebral Column 
of the Troglodytes Gorilla, Troglodytes niger, Pithecus Satyrus, and different - 
varieties of the Human Race. By Professor Owen, F.R.S., F.Z.S. &c. 
Read September 9, 1851. 
IN the communication I had the honour to make to the Zoological Society in 1848", 
on the subject of the Gorilla, the results of the comparison of its cranium and dentition 
with those parts in other Anthropoid Apes, and in different varieties of the Human 
race, were recorded ; I now submit the results of the like comparisons carried out in the 
rest of the skeleton. 
The Mandible or Lower Jaw.—Plates XXXI. & XXXII. 
The lower jaw (mandibula) of the Troglodytes Gorilla is one bone in the adult by 
confluence of the two halves at the symphysis, as in all Quadrumana. Each half or 
ramus (Pl, XXXI. fig. 1) shows the usual horizontal and vertical portions; the 
former gradually augmenting in depth as it approaches the latter, where the breadth of 
the bone suddenly increases. ‘The rami diverge from each other, according to lines 
touching the sockets of the canines and the outer side of the condyles, at an angle of 
35°. The length of the jaw, in a straight line from the back part of the condyle to the 
fore part of the symphysis, is 7 inches 4 lines. From the outer side of one condyle to 
that of the other, 5 inches 5 lines. The vertical extent of the rising ramus from the 
summit of the coronoid process is 4 inches 6 lines; the antero-posterior diameter of the 
same ramus is 2 inches 9 lines. The extent of the alveolar series, from the last molar to 
the canine inclusive, is 3 inches 8 lines; this part of the series is longitudinal, almost 
straight, with a very slight bend inwards, and is parallel with the same part on the 
opposite side. The incisive alveoli are at right angles to the above, and unite them 
together across the fore part of the jaw. The number of the alveoli corresponds of 
course with that of the teeth described in a former Memoir*. The socket of the canine 
is the largest and deepest depression: those of the molars and anterior premolar are 
nearly equal: that of the posterior premolar is much smaller; and those of the incisors 
the smallest of all. 
The symphysis curves from the incisive alveoli downwards and backwards with a 
gentle convexity to the lower border of the jaw. Its exterior surface is smooth and 
convex ; rather more prominent near the middle of its lower part, but devoid of vertical or: 
transverse ridges or tuberosities. There are slight depressions opposite the interspaces 
' Transactions of the Zoological Society, tom. iii. p. 381. * Vol. ili. p. 395. 
VOL. IV.—PART IV. P 
