186 MR. ST. G. MrVART ON THE SKELETON OF THE PRIMATES. 



not bound anteriorly the surface for the anconceus, but is separated from that surface by 

 a flattened tract of bone interposed (PI. XXXVIII. fig. 4) between it and the ridge 

 which does so hmit the anconeal surface. 



The olecranon process is small and scarcely broader relatively than in Man, and, as in 

 him, it does not project so much ulnad as it does in Troglodytes. It is not in any way so 

 prominent as in that genus, being even less so than in Man (PI. XXXVIII. figs. 2 & 6). 



The greater sigmoid ca^dty (PI. XXXVIII. fig. 1 g) is formed nearly as in Man, except 

 that it is broader in proportion to its length than in him, or indeed than in Troglodytes. 

 The lesser sigmoid cavity is less extended from above downwards, and more from behind 

 forwards, than in the Gorilla, thus resembling more the form it presents in Man and the 

 Chimpanzee. 



The coronoid process is broader both absolutely and in proportion to its projection 

 forward than in the two last-named forms, and it is' also relatively broader than it is 

 sometimes in the Gorilla. 



The tubercle for the flexor suhlimis digitorum is, as in the Gorilla^, well developed. 



The fossa for the brachialis anticus is very marked and deeper than in Man or the 

 Chimpanzee, or than is sometimes the case in the Gorilla (PL XXXVIII. fig. I c). 



The fossa for the anconceus is much smaller relatively than in Man, and is less defined 

 anteriorly by the ridge running .downwards and backwards from the hinder end of the 

 lesser sigmoid cavity, that ridge being (as also in the Chimpanzee, but not in the Gorilla) 

 much less marked than in Man. On the other hand the posterior margin of the anconeal 

 fossa is much more sharply defined than in the higher forms (PL XXXVIII. fig. 4_/'). 



As in the Chimpanzee, but not in the Gorilla, the surface for the supinator brevis is 

 much less concave than in Man, and, indeed, is but slightly marked. 



In Man and Troglodytes this surface for the supinator brevis is contiguous for almost 

 its whole extent with that for the anconcens, the surface for the extensor ossis metacarpi 

 pollicis only slightly intervening between them inferiorly. In the Orang, however, a 

 wide flattened tract of bone (serving most probably to give origin in part to the extensors 

 of the poUex) extends up almost to the lesser sigmoid cavity (PL XXXVIII. fig. 4). 

 This tract is bounded in front by the upper end of the external or radial margin of the 

 ulna ; posteriorly it is limited by the ridge running downwards and backwards from the 

 last-named surface (PL XXXVIII. fig. 4 e) and bounding anteriorly the surface for the 

 ancoriceiis. 



At the lower end of the ulna on the inner side of its anterior face is a ridge servinsr 

 to give attachment to the pronator quadratus- (PL XXX'\^III. figs. 1 & 2 x). It is 

 much more marked than in the higher forms. 



As in Troglodytes, the distal articular surface of the shaft of the ulna is relatively 



' See Owen, Trans. Zool. Soc. vol. v. p. 8. 



- Noticed by Pi-ofessor Owen, Trans. Zool. Soc. vol. i. p. 3(54. He refers to Webster and Treadwell's ' Boston 

 Journal of Pbilosophy,' vol. ii. p. 570, and the ' Philosophical Magazine,' vol. Ixviii. p. 186, 1826. 



