MR. ST. G. MIVAET 0]S THE SKELETON OF THE PKIMATES. 191 



S 



Trapezoides. (Plate XLII. figs. 21-23.) 

 As in Troglodytes, the relative extent of this bone from the dorsum of the manus to 

 the palm is very much less in Simia than in Man. The two articular surfaces for the 

 metacarpal of the index are of veiy unequal size — that on the ulnar side being very 

 greatly in excess (PI. XLII. fig. 22 a). The articular facet for the magnum is exceed- 

 ingly small, and confined to the dorsal part of the ulnar side of the bone. That for 

 the intermedium has its greatest diameter transversely extended, instead of from behind 

 forwards {i. e. from dorsum to palm), as has the corresponding surface for the scaphoides 

 in Man (PI. XLII. fig. 23 d). The surface for the trapezium is concave. The proximal 

 radial angle is a little produced, but not so much as is the case in Man. 



Magnum. (Plate XLII. figs. 24-28.) 

 The distal part of this bone is much more transversely extended, as compared with 

 the proximal part, than is the case in Man and Troglodytes ; also there is a more marked 

 lateral constriction below the head. As in the Gorilla\ the antero-posterior (from 

 dorsum to palm) extent of the distal surface is much greater than in Man ; and, again, 

 as in the Gorilla- and also in the Chimpanzee, the radial side of the distal articular 

 surface is strongly notched (PI. XLII. fig. 28 a). On the ulnar side of the same surface 

 is a similar notch, which is much more marked than either in Man or Troglodytes 

 (PI. XLII. fig. 28 h). Indeed this distal articular surface has more the shape of 

 the letter T than it has in the higher forms ; but it resembles that of Troglodytes in 

 being more concave towards its palmar margin than is the case in Man. The head of 

 the bone, as also in Troglodytes, has a more radiad aspect than in Man ; it articulates 

 above with the intermedium and semilunare. As is the case in the higher forms, there 

 is a small articular surface for the metacarpal of the uidex, towards the palmar border 

 of the distal end of the radial face of the bone (PI. XLII. fig. 26 c). The surface for the 

 unciforme is, as ui Troglodytes, more concave from above downwards than is the case 

 in the human magnum. 



Unciforme. (Plate XLII. figs. 29-33.) 



This bone resembles its homologue in Troglodytes, and difiers fi'om that of Man in 

 the large size and more downwai'd production of the palmar process, also in the more 

 acute angle formed by the surface for the magnum with that for the cuneiforme, and 

 in the greater relative extent of the distal surface from before backwards (from tlie 

 dorsum to the palm). 



It differs from that of the Gorilla, as well as from that of Man, in the greater length 

 from above downwards and the less relative transverse extent of the articular surface 

 for the cuneiforme (PI. XLII. fig. 32 c). 



' Trans. Zool. Soc. vol. v. p. 10. ' Loc- at. 



