Mk. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 195 
The internal surface (Pl. XX XIX. fig. 2) looks forwards, but not inwards, thus 
agreeing with the Chimpanzee, and differing from Man and the Gorilla. ‘The part of 
the internal surface which is above the ilio-pectineal line is flat, or with only a very 
slight concavity'; this is sometimes supplemented, however (Pl. XX XIX. 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, in which respect it resembles 
Troglodytes (Pl. XX XIX. fig. 2m). 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 
(Pl. XXXIX. fig. 3) is also more elongated than in Man. 
The crest of the ilium sometimes describes a decided sigmoid curve (P]. 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 all 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 Zroglodytes) no such widening takes place; but 
on the other hand, there is sometimes at the anterior end of the crest (Pl. XX XIX. 
fig. 4 & 5a) avery 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 
(Pl. 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 wide distance between the anterior 
spinous processes causes it to differ much from the form of the anterior margin of the 
ilium of Man (Pl. XX XIX. 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. XX XIX. 
fig. 2 6) is sometimes almost, if not quite, as prominent as in him. Sometimes, however, 
it is not more marked than in 7voglodytes. 
Within this process, and above the acetabulum, the ilium presents a smooth surface 
for the 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 margin 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 the 
‘ M. Duvernoy says “un peu creux,” ‘Archives du Muséum,” vol. viii. p. 28. 
2E2 
