MR. ST. G. MIVAET OiV THE SKELETON OF THE PRIMATES. 195 



The internal surface (Fl. XXXIX. fig. 2) looks forwards, but not inwards, thus 

 agreeing with the Chimpanzee, and differing from Man and the Gorilla. The part of 

 the internal smface which is above the ilio-pectineal line is flat, or with only a very 

 slight concavity' ; this is sometimes supplemented, however (PI. XXXIX. fig. 4), by an 

 inflection of the anterior superior angle of the ilium. The "auricular" surface is more 

 elongated in proportion to its breadth than in Man, m which respect it resembles 

 Troglodytes (PL XXXIX. fig. 2 m). That part of the internal surface which is beneath 

 the ilio-pectineal line is more convex than in Man and the Gorilla, the ilio-pectineal 

 line itself not being so prominent as in these forms. This part of the inner surface 

 (PI. XXXIX. fig. 3) is also more elongated than in Man. 



The crest of the Uium sometimes describes a decided sigmoid curve (PI. XXXIX. 

 fig. 5), though this is always much less marked than in Man, and is occasionally absent, 

 namely, when the anterior end of the summit of the ilium is not at aU inflected. In Man 

 the crest is enlarged somewhat behind its anterior end, and more or less immediately over 

 the acetabulum. In the Orang (as in Troglodytes) no such widening takes place ; but 

 on the other hand, there is sometimes at the anterior end of the crest (PI. XXXIX. 

 fig. 4 & 5 a) a very marked enlargement, which may answer to the one above-mentioned 

 of Man ; and if so, we may imagine that part of the ilium which in Man is anterior to 

 it, to be altogether absent in the Orang. As in the higher forms, so also in Simia, 

 the crest is always enlarged at its posterior end ; but the crest, as a whole, is (as in 

 Troglodytes) narrower in proportion to its length than in Man. The vertical curvature 

 (as in the Chimpanzee) is much less than in Man or the Gorilla; but the crest is 

 produced upwards somewhat suddenly at about the anterior end of its posterior third 

 (PI. XXXIX. fig. 1). 



The anterior margin of the ilium is always concave, and often more so than in 

 Troglodytes, though, as in the latter genus, the Avide distance between the anterior 

 spinous processes causes it to differ much from the form of the anterior margin of the 

 ilium of Man (PI. XXXIX. fig. 2). 



As in Troglodytes, the anterior superior spinous process in Simia is not so marked 

 and distinct a process as in Man; but the anterior inferior spinous process (PL XXXIX. 

 fig. 2 b) is sometimes almost, if not quite, as prominent as in him. Sometimes, however, 

 it is not more marked than in Troglodytes. 



AVithin this process, and above the acetabulum, the ilium presents a smooth surface 

 for t\ie psoas and iliacus muscles; and no ilio-pectineal prominence marks the junction 

 of the ilium with the pubis. 



The upper part of the posterior margin of the ilium is, on the whole, nearly straight 



to the lower margm of the auricular surface ; and though its outline is irregular, there 



is scarcely any trace of the concavity which exists in Man between the posterior 



termination of the crest of the ilium (or posterior superior spinous process) and tlie 



' M. Duvernoy says " un peu creux,'" ' Archives du Museum,' vol. \m. p. 2S. 



2e2 



