202 ME. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 



(PI. XLI. fig. 4 ?■), and, as in Troglodytes, is more rounded and less antero-posteriorly 

 elongated than in Man. 



Of the two articular surfaces for the condyles of the femur, the internal one has its 

 inner margin (as in the Gorilla and Chimpanzee) more convex and prominent than in 

 Man (PI. XLI. fig. 8) ; and the concavity of its surface is mainly produced, as Professor 

 Owen remarks of the Gorilla', by the elevation of that part of it which joins the spine. 



The external articular surface (for the external condyle of the femur), though more 

 convex antero-posteriorly than in INIan, is less so than in the Gorilla ; and sometimes, 

 indeed, it is decidedly, though very slightly, concave antero-posteriorly. 



The spine is also more human in its form than it is in either Troglodyte, being 

 almost as bifid as in Man ; while the groove which descends backwards from its apex, 

 and divides the posterior ends of the articular surfaces for the condyles, is considerably 

 deeper, and more marked than in any of the higher forms (PI. XLI. figs. 2 & 8). 



The lower end of the tibia is inclined so that the anterior margin of its distal end is 

 much more oblique (downwards and tibiad) than in Troglodi/tes, and very much more 

 so than in the human tibia. This obliquity arises from the large size of the lower 

 articular surface for the fibula, and from the inclination inwards of the articular surface 

 of the tibial malleolus. 



The inner*, or free, surface of the last-named process projects more strongly tibiad 

 than in Troglodytes — the inner surface of the shaft immediately above it being more 

 concave vertically than in that genus, though scarcely more so than in Man. 



'The anterior margin of the distal end of the tibia is more prominent than in the 

 higher forms, the surface of the shaft just above it being more concave, vertically, than 

 in them. 



The distal end of the posterior surface of the tibia has a deeper groove for the tibialis 

 jMsticus and flexor longus halhicis than I have observed in any of the higher forms 

 (PL XLL fig. 2^). 



As in Troglodytes, so also in Simia, the tibial malleolus is more truncated at its apex 

 than is the case in Man. 



The distal ai-ticular surface of the shaft of the tibia (PI. XLT. fig. 9) is, as in the 

 Chimpanzee-, far more convex transversely than in the Gorilla or in Man. On either 

 side of the strong median convexity there is (also as in the Chimpanzee) a slight 

 transverse concavity; but the whole surface presents only a mere trace of an antero- 

 posterior concavity, while, as in Troglodytes, its anterior margin descends as much (when 

 the shaft is vertical) as does its posterior margin, instead of, as in Man, the latter margin 

 descending further than the anterior one. 



The articular surface on the outer (peroneal) side of the malleolus foi'ms a more 

 open angle with the distal surface of the shaft than even in Troglodytes, and its vertical 

 extent is also much less (PI. XLI. fig. 1). 



' Trans. Zool. Soc. vol. v. p. 19. - Owen, Im. fit. p. 20. 



