334 
ME. ST. GEORGE MI V ART ON THE SKELETON OE THE PRIMATES. 
This surface is most concave in Hylobates, the lowest Simiidte, the Cebinae, and 
Mycetes, less so in the other forms, and least of all in the Nycticebinae, Tarsius, and 
Cheiromys, where there is either no external concavity at all, or only a very slight one 
near the crest of the ilium. 
In the Nycticebinae, Galago, and Tarsius, the part homologous with the outer 
surface of the ilium of the Anthropoidea becomes exceedingly small, as it forms only 
that part of the actual outer surface which is on the dorsal side of the oblique ridge, 
extending to the acetabulum, before mentioned (Plate XIII. fig. 3, m). 
The internal surface of the ilium is generally narrow and flat, or only slightly concave. 
In none besides Man is it very wide, very concave, and directed entirely inwards. It is 
strongly concave in the Gorilla, however, and there is a very slight concavity in the Simiinae 
generally, and sometimes in Cynocephalus, the Cebinae, Mycetes, Hapale, and Indris. 
In the Nycticebinae and Tarsius this surface is actually convex, by reason of the pro- 
minent ilio-pectineal line; but in Lemur, Galago, and Cheiromys the projecting spinous 
process near the acetabulum produces a concavity between that process and the ilio- 
pectineal line. 
In the lower Cebidae and Hapale the iliac fossa is extremely narrow. 
The wall of the true pelvis, formed by the ischium, is generally elongated and narrow, 
but in Man and the Nycticebinae (especially Loris) it is broad and short. 
The auricular surface generally extends nearly to the crest of the ilium, and is especially 
high in the Cebidae, the Nycticebinae, and Tarsius. It is more distant from it in Man, 
Troglodytes, and Simia, and very much so in Lemur and Indris. 
The ilio-pectineal line generally abuts against the first sacral vertebra, but sometimes 
against the second (as in Hylobates, Pithecia, and Chrysothrix), or between the two (as 
in some Cebidae). In certain forms a ridge continues on as far as the crest of the ilium, 
ending near the part answering to the anterior superior spinous process of Man. This 
ridge is very marked in Indris and Lemur ; and in Galago, the Nycticebinae, and Tarsius 
it forms, as has been said, the actual ventral margin of the ilium (Plate XIII. fig. 3). 
In Cebus the end of this ridge projects as a distinct and prominent process from the 
ventral end of the crest of the ilium, and a similar development is more or less marked 
in the lower Cebidae and in Plapale. 
The ileo-pectineal eminence is moderately marked in Man, as a rounded prominence. 
In Troglodytes it is sometimes absent, sometimes present as a distinct process, though 
more distant from the acetabulum, and nearer the symphysis, than in Man. In the 
Orang it is very large *, but in Hylobates there is only a slight ileo-pectineal prominence 
like that of Man. In the other Simiidae it is not marked, except rarely in Cyno- 
cephalus. 
In Mycetes there is sometimes a remarkable process, but it is not constant f, and in 
* This is perhaps rather the spine of the pubis than an ilio-pectineal eminence. 
f Present in the specimen in the Museum of the Royal College of Surgeons. That at the British Museum 
presents merely a truce of it. 
