186 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
not bound anteriorly the surface for the anconeus, but is separated from that surface by 
a flattened tract of bone interposed (Pl. XXXVIII. fig. 4) between it and the ridge 
which does so limit 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 Zroglodytes. tis not in any way so 
prominent as in that genus, being even less so than in Man (Pl. XX XVIII. figs. 2 & 6). 
The greater sigmoid cavity (Pl. XXXVIIL fig. 1 7) 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 flewor sublimis 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. XX XVIII. fig. 1 ¢). 
The fossa for the anconeus 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 (P]. XX XVIII. fig. 4f). 
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 Zroglodytes this surface for the supinator brevis is contiguous for almost 
its whole extent with that for the anconwus, the surface for the extensor ossis metacarpt 
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 pollex) extends up almost to the lesser sigmoid cavity (Pl. XX XVIII. 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. XX XVIII. fig. 4¢) and bounding anteriorly the surface for the 
anconcus. 
At the lower end of the ulna on the inner side of its anterior face is a ridge serving 
to give attachment to the pronator quadratus’ (Pl. XXXVIII. figs. 1 & 2a). 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 
1 See Owen, Trans. Zool. Soc. vol. y. p. 8. 
> Noticed by Professor Owen, Trans. Zool. Soe. vol. i. p. 364. He refers to Webster and Treadwell’s ‘ Boston 
Journal of Philosophy,’ vol. ii. p. 570, and the ‘ Philosophical Magazine,’ vol. Lxviii. p. 186, 1826, 
