PHYLOGENY OF THE PALHOGNATHA AND NEOGNATILE: 231 
of the free end of the pubis with the ischium, both in Rhea and Struthio, and only in 
these. 
The pelvic girdle of Apterya resembles that of Dromeus and Caswarius in some 
respects. This is what we should expect, since Dromeus probably represents the 
ground form from which the other Palwognathw have been derived. 
In the extraordinary relative length of the pre-acetabular ilium Apferya stands 
alone. It extends forward so as to overlap some four thoracic ribs. The post- 
acetabular ilium is as short relatively as the pre-acetabular is long; it never exceeds 
half the length of the pre-ilium. Asin Struthio, the post-ilium and ischium are widely 
separated, but the separation is more marked since the backward rotation of the 
ischium is somewhat less than in Struthio. 
The innominates meet in the mid-dorsal line as in Rhea, but with this difference: 
whereas in Rhea although the median borders meet, yet a dorsal plane is present as a 
Widening out and flattening of that portion of the dorsal aspect of the pelvis which lies 
between the supra-trochanteric processes, in Apteryx these dorso-median edges meet 
along their whole length, save in the region of the sacrum proper, where a narrow. 
chink reveals the presence of some three neural spines. There is no supra-trochanteric 
process, but the ilia meet in the middle line to form a long knife-like ridge. The 
fovea iliaca anterior extends backwards into the post-acetabular ilium, terminating 
caudad of the anti-trochanter. Behind the acetabulum the vertebral column is bent 
sharply downwards, and has undergone great lateral compression, so that the centra 
of the vertebre have become vertically compressed plates but little thicker than their 
neural spines. Furthermore, owing to the downward flexure of the posterior synsacral 
vertebre the post-acetabular ilia have come to embrace the neural spines of the 
vertebre instead of the centra. The synsacrum extends, moreover, by a single vertebra 
beyond the level of the free (caudad) end of the post-acetabular ilium. 
The ischium is a relatively long flattened blade, forming a wider angle with the 
ilium than in any other of the Ratite. 
The pubis is slender, with a more or less well-marked ventral curve. Caudad, its 
free end may touch the postero-ventral angle of the ischium, but it never fuses 
therewith. ; 
The obturator foramen and fissure are confluent. 
The pectineal process is large and pointed, and formed in part by the descending 
process of the ilium and in part by the pubis. 
Specific differences in the pelves of Apterya are, as Beddard has already shown, very 
slight. According to him the pectineal process is shorter in A. owen? than in 
A. australis. In our specimens if there is any real difference the reverse would appear 
to be the case. I have managed to find sufficient differences to construct a key for the 
species, though with difficulty. Mr. Beddard has already shown that the width across 
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