MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 201 
Patella. (Plate XL. figs. 8 & 9.) 
The patella of the Orang has its surface marked with vertical grooves, as in Man, 
but it agrees with that of Zroglodytes and differs from the human patella in being 
nore rounded and without the produced inferior apex, in having no median vertical 
projection on its posterior surface, and in the subequality of thickness of its outer and 
inner edges, as well as of its superior and inferior ones. 
It differs from that of all the higher forms in its greater breadth, in the less convexity 
of its outer surface, in the almost complete flatness of its inner surface’, and in its 
smaller size, as compared with the adjoining ends of the femur and tibia. 
Tibia. (Plate XLI. figs. 1-5, 8, 9.) 
The length of the tibia, as compared with that of the spine, is much as in 7'roglodytes, 
and nearly one-fifth less than in Man. The proportion borne by it to the femur I have 
found larger than in the Chimpanzee or Gorilla. As compared with the radius, the tibia 
of the Orang is much shorter than that of Zroglodytes; but yet the difference is much 
less than between the latter genus and Man, in whom the tibia is about half as long 
again as is the radius. 
Besides the relative length of the bone, the Orang differs from Man and agrees with 
Troglodytes in the great relative width and less lateral compression of the tibia, in the 
convexity, vertically, of its anterior surface, the vertical concavity of its outer or 
peroneal surface (Pl. XLI. fig. 1), the shortness and bluntness of the crest, and the 
more rounded form of the shaft, which renders it somewhat difficult to describe 
according to the three surfaces and three margins which exist in Man. 
As also in 7'rroglodytes’, the transverse diameter of the superior surface is greater, 
compared with the antero-posterior diameter of the same, than is the case in Man. 
In the greater projection, tibiad, of the internal tuberosity and in the stronger vertical 
concavity of the inner surface of the bone leading down from it to the shaft, the Orang 
resembles the Chimpanzee, and differs from the Gorilla, and still more from Man. 
The tubercle, as also in 7roglodytes, is less prominent than in Man; but there is some 
individual variation in this respect. 
The external tuberosity is at least as large as, if not larger than, the internal one; 
and its thickness between the articular surface for the femur and that for the fibula is 
(Pl. XLI. fig. 2), as also in 7roglodytes, relatively, and often absolutely, greater than in 
Man. The latter articular surface, again, as in 7'roglodytes, is also larger relatively 
than in Man (Pl. XLI. fig. 5), but it is flat, instead of, as in the Gorilla, strongly 
convex. 
The groove for the tendon of the popliteus is very slightly marked; but the depres- 
sion for the semimembranosus (behind the internal tuberosity) is very much so 
? W. Vrolik, ‘ Recherches d’Anat. Comp. sur le Chimpansé,’ p. 15. 
* Owen, Trans. Zool. Soc. vol. v. p. 19. 
VOL. VI.—PART IV. 
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