The ilium is divided, as usual, into two parts by the ridge on its upper or outer surface (ib. fig. 2, _r_), extending obliquely backward to behind the acetabulum—the anterior division being narrower and concave, the posterior broader and convex but in a minor degree. The anterior (slightly thickened) border of the ilium is curved with the convexity forward, extending 8 or 9 lines in advance of the fore part of the neural spine of the first sacral vertebra. The ilia almost meet above that of the second and third sacrals, with which they coalesce, and then diverge to the oblique boundary ridge, which is thence continued, in some with an angular bend, more directly outward. At this angle the bone is so confluent with the sacrum that the orifices leading to the ileoneural canals[26] are almost or quite obliterated. These canals are, here (ib. _i ï_), the longitudinally extended cavities intercepted between the fore parts of the ilia and the continuous coalesced sacral spines and diapophyses, widening to their anterior outlets. The extent of that part of the ilium in advance of the acetabulum is 3 inches 8 lines; the breadth at its middle part is 2 inches. As the ilium approaches the acetabulum it increases in thickness, and is grooved at the outer margin by a vessel which leaves impressions of its ramifications upon the upper concave surface of the bone (ib. fig. 2, +62+). The acetabulum (ib. _a a_) is circular, 11 lines in the diameter of its outlet, 9 or 10 lines in that of its inner circumference, being widely open, as usual in birds, towards the cavity of the pelvis; the trochanterian surface (ib. _t t_) above the acetabulum is elliptic, with the long axis lengthwise, 9 lines by 6 in its diameter, with its upper border sharp and produced; the anterior border (ib. _b_) of the acetabulum is slightly produced; the position of this articular cavity is about midway between the fore and hind ends of the pelvis. The oblique external ridge of the ilium terminates in the outer margin of the broader part of the bone (ib. _r′_), 7 lines above the sharp and prominent margin of the trochanterian surface (ib. _t_). The ilia have diverged from each other for the extent of an inch and a half behind the beginning of the boundary line (ib. _r_), which interval is occupied exteriorly by lateral ossification from the neural spines to the diapophyses of that part of the sacrum: the mesial borders of the ilia (ib. fig. 2, 62′) slightly converge to the fifteenth sacral vertebra, where they are separated by an interspace of 1 inch, and then again diverge to the last sacral; they coalesce with the diapophyses (ib. fig. 2, _d_ _d_). The inner or under surface of the ilium is thickened into a kind of buttress (ib. fig. 1, _e_), terminating behind the ischiadic foramen. The breadth of the iliac bones and intervening sacrals, 1 inch behind the acetabulum, is 5 inches; at the back part of the pelvis it is 4 inches. The outer border of the posterior part of the ilium (ib.