184 ME. ST. G. MIVART OX THE SKELETON OF THE PEIMATES. 



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 poUex ; 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 siqnnator 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 tiiberosity is much less prominent than in Man ; but its surface is more 

 excavated, and, as in Troglodytes, is much more ulnad in position (PL XXXVII. fig. 6 b). 



The bone is not so contracted at its neck as in ]\Ian 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 very prominent and rough surface 

 (PI. XXXVII. fig. 5 a) for the insertion of the siqnnator longus. The styloid process 

 itseKis not so pointed as in Man and Troglodytes (PI. XXXVII. fig. 5/). 



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 jjollicis and that for the extensor ossis 

 metacarjii j)ollicis (PI. XXXVII. figs. G & 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 (PI. XXXVII. fig. 6(/). 



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 (PI. XXXVII. fig. 8). 



Ulna. (Plate XXXVIII.) 

 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 (PI. XXXVIII. fig. 1), 



' Owen, Trans. Zool. Soc. vol. v. p. 7. 



