192 ME. ST. G. MIVAET ON THE SKELETON OF THE PEIMATES. 



Metacaifus. 



The length of this segment of the hmb (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 tliat of the entire manus, 

 is very much the same as in Troglodytes, 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 (PI. XLII. figs. 38 & 42) of those palmar tuberosities 

 and ridges at the divergence of the interossei which are so marked in Troglodytes, 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 fossae 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 ihejlexor carpi 

 radialis (PI. 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 contmued between the lower 

 facet for the third metacarpal and the articular surface for the trapezoides. The ulnar 

 ' Owen, Trans. Zool. Soc. toI. t. p. 11. - Owen, he. cit. 



