The =ilium= is nearly parallel with the median plane and its axis is
only slightly oblique with regard to the horizontal plane. The gluteal
surface is concave. The iliac surface is almost flat. The auricular
surface faces almost directly inward, and in front of it there is an
extensive rough area. The ilio-pectineal line is very distinct and is
uninterrupted. The anterior border or crest is strongly convex, thick,
and rough. The internal angle is represented by a thickened part which
bears two eminences, homologous with the posterior superior and
posterior inferior iliac spines of man. The external angle also has two
prominences, which are equivalent to the two anterior spines present in
man. The shaft is almost sagittal and is compressed laterally. Above it
is smooth and rounded, and below it bears a crest externally which
terminates at a tuberosity in front of the acetabulum.
The =ischium= has a twisted appearance owing to the fact that its
acetabular part is nearly sagittal while the posterior part is almost
horizontal. The two bones also diverge behind and the tubera are
flattened and everted. The superior ischiatic spine is low and thick;
its posterior part is marked by transverse grooves and has a prominent
outer lip. There is no lesser sciatic notch. The ischial arch is
relatively small and is semi-elliptical.
[Illustration: