﻿76 



FOSSIL REPTILIA OF THE 



The ischia of Omosaurus being thus determined, the homology of the other pair of 

 pelvic bones (PI. XX, figs. 4 and 5), wrought out of the mass of matrix overlying the 

 haemal surface of the sacrum and ilia, was plain. They confirm the opinion of Professor 



Leidy as to the nature of the bone ; and, so far as their dislocated condition indicated 

 their natural direction, it supports the conclusion of Professor Cope that they had " a 

 position similar to those in the Crocodilia" i. e., directed forward and downward, as 

 shown by Cuvier, in the ' Ossemens Fossiles,' tome v (1824), PL IV, fig. 15, a, PI. V, 

 fig. 6, and as exemplified in my diagram, p. 76, Fig. 13. 



So much of the homological ground being thus cleared, we may pass to the question 

 of the affinities it brings into view. 



In birds, as a rule, the pubis is a long simple style without process (fig. 15, ' Bird ') ; the 

 exceptions are chiefly seen in the wingless forms, Apteryx, e. g., and the Cassowary, in 

 which latter bird the expanded acetabular end of the pubis projects forward beyond 



