8 Osteological Studies of the Subfamily Ardeiuee. 
grooves and making one rounded summit for this part of the 
bone. 
The anterior margins of the ilia are notched and scalloped, 
and bordered by a somewhat deep and slightly raised emargina- 
tion. Where these bones are broadest in front, the lateral edges 
are quite sharp, but as the pelvis contracts in width as we near 
the acetabulae they become rounded and smooth. The iliac sur¬ 
face, on either side, thus bounded, is at first directed upwards and 
outwards, but as we approach either actabulum, this surface 
gradually comes to look almost directly outwards. Ilio-neural 
grooves exist between the anterior forks of the gluteal ridges, for 
some little distance, before these latter, and well defined crests, 
are lost anteriorly (Fig. 13). 
Few traces or markings are left upon the inner margins of 
the post-acetabular surfaces, to define the boundaries which origin¬ 
ally existed between the vertebrae and the iliac bones ; they are 
best seen behind. For the most part though, the pelvic roof has 
become in the adult, one unbroken surface—a very smooth and 
firmly ossified tract. 
The outer angles of the gluteal ridges are rounded and pro¬ 
ject immediately over the antitrochanter, on either side, from 
which point each ridge runs almost directly backwards to the 
hinder margin of the bone. This latter, as a whole, is concave 
towards the posterior aspect, and from its outer angles the curved 
and inturned pubic bones may be seen pointing towards each 
other, their tips some 2 centimetres apart. 
Only a limited part of the surface of either ischium can be 
discerned from this superior view, as these bones behind are nearly 
at right angles with the overhanging ilia. 
Among all the Ardeince that I have had the opportunity to 
examine, the post-acetabular surface is about equal in extent with 
the pre-acetabuler area. In the former the general surface is con¬ 
vex, while in the latter it is concave ; the boundary between them 
I place, in common with Owen, at the line of the gluteal ridge. 
The post-acetabular surface slopes downwards from a line joining 
the outer gluteal angles ; the amount of which declination can 
best be appreciated by a glance at my figure of the side view of 
this pelvic bone (Fig. 14). 
Upon lateral aspect the centra of the leading vertebrae may 
be seen below the eaves of the iliac roof, and some idea gained of 
