184 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
though the concavity which is in him produced by the projection forwards of the distal 
margin of the bone is wanting, that margin in the Orang, as also in Troglodytes, not 
being similarly prominent. 
The posterior surface presents but a very slight flatness for the origin of the extensors 
of the pollex ; and sometimes, indeed, there is no flattening perceptible. The external 
surface, which generally in Simia passes insensibly into the posterior one, presents a 
rough tract and a slight excavation for the supinator teres, extending downwards nearly 
to the middle of the bone. 
Of the three margins which exist in Man, the posterior one is, in the Orang, never 
more than faintly marked, and that only towards the middle of the bone. 
The external margin of the radius of Man may be said to have disappeared altogether 
in the Orang; but the internal margin, for the interosseous ligament, is distinctly 
marked, though it is never nearly so sharply projecting as in him and the Chimpanzee, 
and scarcely so much so as in the Gorilla. 
The bicipital tuberosity is much less prominent than in Man; but its surface is more 
excavated, and, as in Troglodytes, is much more ulnad in position (P]. XX XVIL fig. 6 4). 
The bone is not so contracted at its neck as in Man and the Chimpanzee, and the 
rim or margin’ of the head is not so sharply marked inferiorly as in them, the Orang 
in these points resembling the Gorilla. The proximal articular surface of the head is 
less concave than in the human radius. 
A little above the styloid process there is a yery prominent and rough surface 
(Pl. XX XVII. fig. 5 a) for the insertion of the supinator longus. The styloid process 
itself is not so pointed as in Man and Troglodytes (Pl. XX XVII. fig. 5f). 
The grooves for the extensor tendons are quite similar to those of Man, except that 
they are sometimes more marked than in him; and this is even the case with the 
groove for the extensor secundi internodii pollicis and that for the eatensor ossis 
metacarpi pollicis (Pl. XX XVII. figs. 6 & 7). 
- The articular surface for the reception of the ulna looks more backwards than in 
Man, especially when the ulnar angle of the anterior side of the distal end of the bone 
is much produced forward and ulnad, as is sometimes the case (Pl. XX XVII. fig. 69). 
The carpal surface at the inferior end of the bone has the internal quadrate surface 
for the semilunare larger, in comparison with the triangular one for the scaphoides, 
than is the case in Man (Pl. XX XVII. fig. 8). 
Uina, (Plate XXXVIIL.) 
This bone, which, unlike the radius, seems in the Orang to be constantly longer than 
the humerus, bears much the same proportion to the ulna of Man and Troglodytes that 
the radius of the Orang bears to the radius of those forms. 
When its anterior (flexor) surface is opposite the observer (Pl. XXXVIII. fig. 1), 
1 Owen, Trans. Zool. Soe. yol. y. p. 7. 
