52 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
by M. De Pauw, the excellent Contréleur des Ateliers of the 
Musée. 
M. Dollo adopts the erect attitude of Jywanodon ; and for this he 
adduces reasons which claim attentive consideration. Time will not 
allow me here to do justice to them, and I must refer those who 
are interested in this vexed question to Dollo’s memoir. 
The undisturbed natural association of the pelvic bones in some 
-of the Bernissart skeletons has enabled Dollo to give an excellent side 
view of the pelvis in J. bernissartensis, Blgr. Its accuracy is unim- 
peachable. In its essential features it is in accord with the resto- 
ration of the pelvis of Z. Mantellz, which, in June 1875, I submitted 
‘to the Society ; but there are some details which the better preserva- 
‘tion of the Bernissart fossils has enabled Dollo to correct. Thus 
the direction of the preacetabular part of the os pubis (prepubis of 
.Marsh), which I had originally imagined to have an inward curve, 
Dollo shows to be curved outwards. The foramen at the point where 
the post-acetabular part of the pubis (post-pubis of Marsh) diverges — 
from the body of this bone, and which I had identified with the 
uppermost opening in the bird’s obturator foramen, and suggested 
that it might, in Jguanodon, asin the bird, transmit the tendon of the 
Obturator internus muscle, M. Dollo interprets differently. He 
shows that the ischiatic half is contributed by the ischio-pubic 
border of the body of the ischium, and that it is not, as I had 
wrongly supposed from my less perfect material, contributed by the 
obturator process of the shaft of the ischium. 
M. Dollo believes the larger opening, marked i. in his figure, 
to be the homologue of that which in the bird transmits the 
Internal obturator tendon, basing this belief on the identification of 
the process given off from the ventral border of the ischium, beyond 
the neck of this bone in [yuanodon, with that present in some birds, 
notably Ratite. The small foramen next the acetabulum, marked i., 
‘he homologizes with a depression which he observed in the chicken 
above that for the obturator tendon. This J have not succeeded in 
discovering in Struthio and Ehea, birds which I selected on account of 
their well-developed ischiatic obturator process, and the completeness 
of the upper foramen which (11. in Dollo’s figures) this process makes 
by its union with the postacetabular part of the os pubis. 
[ Note.—In discussing the homologies of these foramina in reptiles 
and birds it is needful to bear in mind that the term obturator foramen 
has been applied to very different apertures. Thusit has been given 
to the aperture by which the obturator nerve leaves the pelvis, and 
also to the space lying between the os pubis and the ischium ; now in 
lizards the nerve pierces the os pubis by an opening entirely within this 
bone, and it does not pass through the ischio-pubie interval; in 
Chelonians, however, it takes this latter course ; in Crocodiles also it 
passes through the angle formed by the divergent pubis and ischium. 
In birds it also passes out between these bones, yet not through the 
aperture nearest to the acetabulum, but at a lower point, piercing 
the obturator membrane below the obt.-ischiatic process (thea). It 
would be more exact to define the foramen with reference to the 
