54 PROCEEDINGS OF THE GEOLOGICAL SOCIRFTY. 
difficulty that at first sight appears, in consequence of their different 
direction, in homologizing these with the pubis in the Lizard, 
will disappear when it is remembered that in the embryo bird the 
os pubis and the ischium are directed at a right angle to the long 
axis of the ilium, which is nearly the direction of these bones in 
the Lizard. 
To what part, if any, of the pubis in other vertebrates is the 
prepubis in Dinosanria (Jguanodon) the morphological equiva- 
lent? In birds its equivalent has been thought to be the angular 
tubercle or spur which projects from the front border of the ace- 
tabulum. This is well marked in the Ostrich and the Apteryx. In 
Dollo’s figure of the pelvis of the chick, it les in front of the snture 
which indicates the anterior limit of the acetabular contribution of 
the (post-) pubis, separated from this by a distinct interval. Such 
a disposition would place this tubercle, or spur, completely within 
the ilium ; and were this so, it would constitute a strong argument 
against regarding it as the homologue of the Dinosaurian prepubis. 
Gegenbaur, however, represents, in the chick, the ilio-pubic suture 
as passing through the tubercle; and this is its situation in 
Apteryx (fig. 5), and in Rhea, immature individuals of which I ex- 
Fig. 5.— Pelvis of Anteryx. (Original from a specimen in the 
Middlesex-Hospital Museum.) 
Il. Liium. Isch, Ischium. pub. Pre-pubis. i pp. Post-pubis. 
amined with reference to this point: the tubercle is manifestly that 
known to anatomists as the ilio-pectineal eminence, tuberculum ilio- 
pectineum, tub. ilio-pubicum, of higher vertebrates. Its dual com- 
position in birds, though it seems to weaken the supposition of its 
