MR. ST. G. MIVAET 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 Troglodytes and differs from the human patella in being 

 more 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, ^'s much as in Troglodytes, 

 and nearly one-fifth less than in Man. The proportion borne by it to the femur 1 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 Troglodytes ; but yet the difierence 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 (PI. 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 Troglodytes', 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 Crang 

 resembles the Chimpanzee, and differs from the Gorilla, and still more from Man. 



The tubercle, as also in Troglodytes, 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 

 (PI. XLI. fig. 2), as also in Troglodytes, relatively, and often absolutely, greater than in 

 Man. The latter articular surface, again, as in Troglodytes, is also larger relatively 

 than in Man (PI. XLI. fig. 5 k), 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. siir Ic Chimpanse,' p. 15. 

 - Owen, Trans. Zool. Soo. vol. v. p. li). 

 VOL. VI. — PART IV. 2 F 



