192 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
Metacarpus. 
The length of this segment of the limb (estimated by the third metacarpal), compared 
with that of the spine, is greater than in any higher species, namely about 18-2 to 100. 
The relative length of the same metacarpal, as compared with that of the entire manus, 
is very much the same as in 7roglodytes, namely about 39 to 100, and greater than 
in Man, in whom I have found it to be about 34:6 to 100. 
The four outer Metacarpals. 
As in the higher forms, these metacarpals in the Orang are thicker at each end than 
in the shaft; the distal extremities are wider than the proximal ends (though not so 
much so as in the Gorilla), and the shafts slightly broader distally. 
The heads have their antero-posterior diameter (from dorsum to palm) about equal 
to their transverse dimensions. 
The shafts are much elongated; and these metacarpals in the Orang are like the 
Chimpanzee’s, and are more slender than those of the Gorilla or of Man. The shafts are 
also more rounded than in the higher forms, the dorsal flattening being less marked, 
while there are only faint traces (Pl. XLII. figs. 38 & 42) of those palmar tuberosities 
and ridges at the divergence of the interossei which are so marked in 7’voglodytes, espe- 
cially in the Gorilla’. The processes on each side of the proximal ends of the palmar 
surfaces of the heads are much less marked than in any higher forms, especially than 
in Troglodytes. 'The fosse on the sides of the heads are also less marked than in that 
genus. These metacarpals increase, not only in length but also in projection distad, 
from the fifth to the second successively. 
First Metacarpal. (Plate XLII. figs. 35 & 36.) 
This metacarpal presents a saddle-shaped surface for the trapezium, very like that of 
Man. ‘The proximal prominence on the palmar side is less enlarged than in Troglodytes? ; 
and the whole bone is more bent, with the concavity palmad, than in the higher forms. 
The shaft is sometimes slightly as it were twisted on its long axis. 
Second Metacarpal. (Plate XLII. figs. 37-40.) 
The shaft of this metacarpal is also somewhat twisted, and it is concave radiad. Its 
proximal end, like that of the same bone in the Gorilla, does not, as in Man and the 
Chimpanzee, bifurcate for the reception of the trapezoides ; and its proximal surface is 
therefore less concave transversely. As in Troglodytes, the tubercle for the flexor carpi 
radialis (Pl. XLII. fig. 38-40, a) is stronger than in Man, but that for the extensor carpi 
radialis longior is not more marked than in him. Between these tubercles there is a 
deep groove (in which vascular foramina open), which is continued between the lower 
facet for the third metacarpal and the articular surface for the trapezoides. The ulnar 
? Owen, Trans. Zool. Soc. vol. v. p. 11. * Owen, loc. cit. 
Pee Se aie 
