PHYLOGENY OF THE PALZOGNATH® AND NEOGNATH &. 229 
closely resembles, at this stage, the permament condition which this bone obtains 
in Struthio. 
The extreme antero-ventral angle of the pre-ilium is sharply defined and produced 
outwards, overlapping the penultimate thoracic rib, with which it ultimately becomes 
completely fused. The innominates meet in the middle line above the synsacrum, 
cephalad and caudad, but leave the neural spines of the synsacrum exposed at the 
bottom of a groove over the sacral region. 
The ischia, which, it will be remembered, in Caswarius approached one another in 
the mid-ventral line, in Rhea actually meet at a point corresponding with a line passing 
downwards from behind the anti-trochanter. From this point backwards they remain 
in close juxtaposition, later in life more or less completely fusing. These approximated 
ischia form a lng backwardly projecting median bar, produced caudad far beyond the 
level of the post-acetabular ilium. Thusa kind of false roof is formed to the abdominal 
cavity and a floor to the renal fossa. 
The pubes, as in Dromeus and to a lesser extent in Casuarius, are bowed outwardly 
and terminate freely near the end of the ischia. 
The pectineal process is formed in part by the descending acetabular process of the 
ilium and partly by the pubis. 
The adult pelvis differs in many respects from that of the nestling, carrying the points 
wherein it is peculiar a stage further in development. 
The supra-trochanteric process now forms a large overhanging ledge, directly above 
the acetabulum. The innominate bones now meet in the mid-dorsal hne throughout 
the whole of their length. ‘The post-acetabular ilium fuses on either side by a broad 
expanded foot with the ischia, and beyond this fusion—a point of contact only in the 
nestling—is continued backwards a long pointed process. ‘The pubes, turning suddenly 
caudad and mesiad, fuse eventually with the ischia. 
The sacral vertebrae in Caswarius lay level with the ventral border of the innominate, 
and extended outwards to articulate with the vertical acetabular process of the ischium. 
In Rhea these vertebre are raised up so as to lie above the level of the acetabulum. 
The post-acetabular ilium, in the nestling Grebe, is subequal in length with the pre- 
acetabula, in the adult it is longer than this, 
In Struthio the pelvis presents one or two points wherein it differs markedly from 
that of the other Palwognathe. 
Like Dromeus, the post-acetabular is longer than the pre-acetabular ilium, only the 
difference is much greater in Struthio. The post-acetabular region remains permanently 
and widely separate from the ischium, and is so narrow in proportion to its length as 
to be almost rod-shaped. ‘The pre-acetabular ilium is relatively as long as in Dromeus. 
The fovea iliaca anterior is rather convex than concave. In this particular Struthio is 
peculiar: since the pre-acetabular ilium instead of being concave externally, so as to, 
on this account, more or less completely embrace the neural spines of the synsacrum, 
VoL. xv.--Part y. No. 16.—December, 1900. 2k 
