228 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
ilium of an exceedingly thin plate of bone with a jagged free edge. It arises in the 
region of the 5th post-sacral vertebra, and is continued backwards from this point. From 
the superior border of the ischium there arises a similar plate of bone of corresponding 
length. In very old birds these two jagged-edged plates nearly meet, foreshadowing 
the formation of the ilio-ischiadic foramen of the Neognathe. 
The interobturator process, both in Caswarius and Dromeus, is well marked. 
The ischia, both in Dromeus and Casuarius, are more or less rod-shaped and 
very distinctly bent inwards towards the middle; this is a point of great significance 
when considered in connection with the ischium of Rhea. The ischium is roughly 
2 -shaped. Its vertical process articulates with (in the young) and eventually 
fuses with the pre-ilium, forming the lower half of the anti-trochanter. Antero- 
ventrally it articulates with and eventually fuses with the pubis, the fusion with the 
pubis taking place much earlier than is the case with the vertical process and the ilium. 
The pubes are very slender relatively, with a strong outward curve in Dromeus and 
Casuarius caswarius, straight or only slightly curved in the remaining species of 
Casuarius. In the nestling they do not extend backwards as far as the level of the 
free end of the post-ilium. In the adult they extend beyond this, reaching nearly to 
the end of the ischia. They are always free posteriorly in the dried skeleton, 
connected by cartilage in the living bird with the ischia. 
The pectineal process seems to be formed for the most part by the descending process 
of the ilium. It reaches its greatest development apparently in Dromeus, but in a 
pelvis of Caswarius casuarius it is only slightly less in size. In the remaining species 
of Casuarius it is but feebly developed. 
The outline of the pre-ilium differs, but the series of adult skeletons in the Museum 
collection is not sufficiently large to enable any reliable data to be drawn from 
comparisons. F 
Specific differences in the form of the pelvis of Caswarius may possibly be found, but 
I think it extremely doubtful. The collection of adult skeletons which forms the 
subject of this paper is not nearly large enough to afford the material necessary for 
such a task. 
The pelves of the C. bennetti group seem distinguishable from the C. caswarius group 
by reason of the relatively longer and narrower post-acetabular ilium. We have 
no adult skeletons of the C. wnappendiculatus group. 
In Rhea the form of the pelvis is unique, but, as will be shown, is probably a direct 
modification of the Dromeine type. 
In the nestling the pre- and post-acetabular ilia are subequal in length. The latter 
is abruptly truncated caudad, and rests by its postero-ventral angle upon the closely 
approximated ischia, to be described presently. The supra-trochanteric process is 
but feebly developed, and the anti-trochanter is but slightly below the level of the 
neural crest of the synsacrum. ‘The post-acetabular ilium is long and narrow and 
