ME. ST. G. MIVABT ON THE SKELETON OF THE PEIMATES. 203 



The articular surface for the lower part of the fibula is much larger than in Man and 

 Troglodytes, being about the same size as the malleolar one for the inner side of the 

 astragalus (PI. XLl. figs. 5 & 9 s). 



The shaft of the tibia is, as in the higher forms, triangular above its middle ; but 

 below that it is, as in Troglodytes, much more rounded than in Man. 



The internal surface is convex, except at its upper part and just within the crest and 

 below the tubercle, in which last situation there is, as also in Troglodytes', a rough 

 and depressed surface (PI. XLI. fig. 1) for the insertion of the sartorius, gracilis, and 

 semitendinosiis muscles. 



The external, or peroneal, surface of the tibia is, as in Troglodytes, more strongly 

 concave above than in Man, while from rather above the middle of the bone, it merges 

 insensibly into the anterior surface. This external surface of the human tibia is much 

 broader from behind forwards than is the part whicli corresponds to it in Simla, if the 

 faint ridge (PI. XLI. fig. 5 /) running downwards from the front of the upper surface 

 for the fibula is that to which tlie interosseous ligament is attached. 



The posterior sm-face of the tibia presents an oblique popliteal ridge, which, however, 

 as also in Troglodytes, is much less strongly marked than in Man. 



The medullary foramen (PI. XLI. fig. 2 n) is much as in Man and the Chimpanzee, 

 and more above the middle of the bone than I have observed it to be in the Gorilla. 



The anterior border, or crest of the tibia, is less sharp, much shorter, and inclines 

 more markedly tibiad below than in Man, agreeing in these points with Troglodytes, 

 except that in Simia the crest is rather more sharp towards its upper end. 



The inner border, as also in Troglodytes, is so little marked as to be hardly distin- 

 guishable, except for a short distance above the posterior border of the malleolus. 



There is a well-marked external or peroneal border, which, however, does not 

 correspond with the external border of the tibia of Man, inasmuch as it descends from 

 behind, and not from in front of, the upper facet for the fibula ; it becomes lost about 

 halfway down the tibia. 



Another and less marked external ridge (PI. XLI. fig. 5 /) appears to correspond with 

 the external margin in Man. It springs from a point anterior to the upper articular 

 surface for the fibula, and descends to the apex of the lower articular surface for that 

 bone. This ridge is rather more strongly marked in Troglodytes. 



Fibula. (Plate XLL figs. 1, 3, G, 7, 10, & 11.) 

 As in Troglodytes^ this bone is much more distant from the shaft of the tibia than in 

 Man; it is also shorter, stouter, and straighter than in him, and has the ridges and 

 depressions on its surface less marked, — in all which points the fibula of the Orang 

 agrees with that of the Gorilla and that of the Chimpanzee. 



The proximal articular surface (PI. XLI. figs. 7 & 10) is more rounded than in 

 ' Owen, Trans. Zool. Soc. rol. v. p. 19. - Owen, he. at. vol. i. p. 300. 



2 F 2 



