﻿KIMMEKIDGE CLAY. 



77 



the joint in a pointed form, about six lines in length. The proximal end of the pubis 

 enters into the formation of the acetabulum in all birds. The distal end terminates, 

 in most birds, freely ; in some it is anchylosed to the ischium ; in the Ostrich it joins its 

 fellow to form a symphysis pubis : l in all it is directed backward and downward. 



Fig. 15. 



A 



Modifications of pubis. The line A A traverses the corresponding part of the bone. 



In the Monotremes the pubis (fig. 15, Ornithorhynchus) sends off from its fore part, 

 about one third of its length from the acetabidar end, a, a low and broad process, c, 

 giving attachment to the outer part of the base of the marsupial bone. It joins its 

 fellow at the expanded distal end, s, and joins at /, the corresponding end of the ischium, 

 thus dividing the obturator interspace into a pair of foramina. As in all mammals 

 the bone is directed downward (hagmad) and a little backward. 



1 For other modifications, which, however, give no belp in the present inquiry, see my ' Anatomy of 

 Vertebrates,' vol. ii, pp. 35, 36. 



