MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 207 



anterior articular surface by a groove for the astragalo-calcaneal ligament. This groove, 

 though somewhat deeper than in Man (PI. XLIII. fig. 9/-), is not nearly so much so as 

 in the Gorilla. 



The anterior articular surface for the os calcis (PI. XLIII. fig. 9 h) is much elongated, 

 and is concavo-convex, but it is not very distinctly marked off from the rest of the 

 articidar sm-face of tlie head of the astragalus. 



NavicuJare. (Plate XLIII. figs. 14-16.) 



This bone in the Orang has a rather more marked jiroximal concavity than has its 

 homologue in the Gorilla, and a much more marked one than that of Man. 



The vertical diameter of the same surface also predominates over the transverse one to 

 a greater degree than in the human naviculare. Shnia agrees with Homo, and differs from 

 Troghdi/fes, in having the plantar end of the bone less antero-posteiiorly expanded ; and 

 the tuberosity (PI. XLIII. fig. 15 e) is less produced than in Man, and much less so than 

 in Troglodijtes. 



The distal articular suiface, as a whole, is naiTower, in proportion to its vertical 

 extent, in the Orang than it is in the Gorilla, and still more so than in Man. It agrees 

 with that of Troglodytes, and diflfers fi-om that of Man in the marked concavity of the 

 surface for the ectocuneiforme (PI. XLIII figs. 14-16 i), and in the convexity of those 

 for the mesocuneiforme and entocuneiforme. Yet the angle formed by the first of these 

 with the surface for the mesocuneiforme is smaller than in the Gorilla, and still more 

 so than in Man. In the Orang there is generally a larger facet (PI. XLIII. fig. 16 e) 

 for the cuboid than in Troglodytes. The rough tract on the peroneal surface of the 

 bone (between the facet for the cuboid and the peroneal margins of the proximal 

 and distal articular surfaces) is much more extensive in the Orang than in Man or 

 Troglodytes (PI. XLIII. fig. 16 d). 



Entocuneiforme. (Plate XLIII. figs. 22-26.) 

 The entocuneiforme of Simia differs much from its homologue in Man or Troqlodytes, 

 its tibial surface being strongly concave, as also the margin connecting the surfaces for 

 the first and second metatarsals. The articular surface for the metatarsal of the hallux 

 has a greater vertical concavity than in any higher species, being sometimes, indeed, truly 

 saddle-shaped (PI. XLIII. fig. 23 & 24 a). Sometimes, however (PI. XLIII. fig 26 a), this 

 vertical concavity is absent. This surface looks rather more tibiad than it does forwards', 

 and it cannot be said to be notched on its inner side — as is the case in Man and Tro- 

 glodytes. The greater part of the anterior aspect of the bone is occupied by a rough 

 non-articular tract which extends upwards and widely separates the surfaces for the 

 first and second metatarsals- (PI. XLIII. figs. 2o-2G c). 



' M. Trolik remarks that it is so placed " que le gros orteil doit s'e'carter dcs autres." ' Rocherchcs d'Anat. 

 Comp.' p. 1.5. ^ Noticed by Professor Huxley, see ' llcdical Times," 1864, vol. i. p. .56,"). 



