IN THE SOCIETY’S COLLECTION. 99 
Exactly in the middle of the anterior border of the pubic portion 
of the innominate bone there is a small thin plate of osseous tissue 
which is connected with the pubis by strong fibrous bands, and which 
is continued anteriorly and superiorly by cartilage for some distance, 
when it becomes continuous with the tendons of the parietal abdo- 
minal muscles, being most connected with the external oblique. 
~ Portions of the external surface of the left pubis and ischium of the Ostrich. The - 
small osseous plate (a) attached to the pubis is represented partly surrounded by 
cartilage. 
In dry skeletons a slight thickening of the anterior border of the 
pubic bone indicates the attachment of this ossification in most; but 
in one of the three skeletons in the British Museum this bone is an- 
chylosed on one side, and Mr. Gerrard has specimens in which both 
are still attached. A diagram of the Ostrich’s pelvis in Mr. Haughton’s 
paper also shows this bone anchylosed, though no mention is made of 
it in his paper. 
It would be extremely interesting to make out the homology of 
this small but perfectly independent ossification. Its relation to the 
muscles of the abdominal wall would favour the idea of its corre- Page 360. 
sponding to the marsupial bone of the Kangaroo and its allies; and 
if that is the case, the whole of the anterior prolongation of the 
Ostrich’s pubis would correspond to the small ridge of bone on 
either side of the superior margin of the symphysis pubis in the 
Mammalia. 
The obturator internus also arises from the superficial surface of 
this bone and its cartilage, as well as from the adjacent surface of 
the ischium and from the pubis, extending so far forward that the 
muscles of the opposite sides are only separated from one another by 
an inch or so at the symphysis pubis. 
H 2 
