MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 191 
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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 Siméa than in Man. ‘The two articular surfaces for the 
metacarpal of the index are of very unequal size—that on the ulnar side being very 
greatly in excess (Pl. XLII. fig. 22a). 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 (7. é. from dorsum to palm), as has the corresponding surface for the scaphoides 
in Man (Pl. XLII. fig. 25d). 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 isa 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 (Pl. XLII. fig. 28a). On the ulnar side of the same surface 
is a similar notch, which is much more marked than either in Man or Troglodytes 
(Pl. XLII. fig. 284). 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 
aboye with the intermedium and semilunare. As is the case in the higher forms, there 
is a small articular surface for the metacarpal of the index, towards the palmar border 
of the distal end of the radial face of the bone (Pl. XLII fig. 26c). The surface for the 
unciforme is, as in Zroglodytes, 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 7’roglodytes, and differs from that of Man in 
the large size and more downward 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 the 
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 (Pl. XLII. fig. 32 ¢). 
' Trans. Zool, Soc. vol. y. p. 10. 2 Loe. cit. 
