ANNIVERSARY ADDEESS OF THE PRESIDENT. 53 
herve, and to give the name ‘“ cordiform” or “ thyroid,” used by 
continental anatomists, to the ischio-pubic interspace. But this 
would do violence to long-established usage here, so that under the 
circumstances it is better, as least liable to create misunderstanding, 
to designate by “obturator” the interspace between the os pubis 
and the ischium without reference to the course taken by the obtu- 
rator nerve. | 
The homologies of the os pubis in the subclass Dinosauria, or rather 
in its order Ornithopoda (Marsh)—for in Sauropoda they do not 
offer any difficulty, which have greatly engaged the attention of 
paleontologists—have been discussed by Dollo ; and since the subject 
is of much interest it claims some notice. 
The conclusion at which Dollo arrives (drawn, it would seem, 
chiefly from a consideration of the pelvis of Allosaurus, Marsh, 
whose restored figure he reproduces, and of the chick) is “ that the 
pubis and the post-pubis are primitively separate elements, and that 
Dinosauria and birds alone possess the latter.” 
Now Marsh tells us that the presence of the post-pubis in Allo- 
saurus was inferred by him from the occurrence of a lower, and 
apparently articular, facet on the pubic border of the ischia; and 
also that he inferred its form from that of Laosaurus. In addition 
to this the delineation of the post-pubis in his figure of Allosaurus 
is by a dotted outline, a method always used by this trustworthy 
- paleontologist, wherever the parts of a figure are not drawn 
from an actual specimen. 
The presence of a ventral symphysial union of the distal ends of 
the pubes in Allosaurus had always made me doubt the presence of 
a post-pubis in this Dinosaurian, because a post-pubis (if present) being 
the homologue of the post-pubis in the bird, and this the homologue 
of the pubis in the Lizard, of which latter the pubis in Allosaurus 
is also the homologue, it must follow that in each half of the pelvis 
of this Dinosaur there would be two bones, each the morphological 
equivalent of the Lacertian pubis, a thing altogether unin- 
telligible. But I gather from his having placed Allosaurus in 
Theriopoda that Marsh himself has abandoned the idea of its possess- 
ing a post-pubis. After this I think I am scarcely putting it too 
strongly when I say that all reasoning from Allosaurus as to the 
interpretation of the (pubis) post-pubis in Dinosauria rests on an 
unproved foundation. 
In Iguanodon, Hypsilophodon (and Omosaurus), in which alone 
I have had an opportunity of studying the os pubis, I have never, 
even in immature individuals, seen any mark of the primitive sepa- 
rateness of the two parts of the os pubis which Marsh distinguished 
by the names pre- and post-pubis ; and this has left me unconvinced 
of such original distinctness in respect of these Dinosaurs; I have 
therefore always used Marsh’s excellent terms as short, convenient 
names by which to refer to the pre- and postacetabular parts of the os 
pubis, without attaching to them the idea of a distinct individuality. 
The homology of the postpubis in Dinosaurs with the pubis of 
birds, first pointed out by ie is very generally accepted. Any. 
¥YOL. XL. 
