Prof. H. G. Seeley on the Ornithosaurian Pelvis. 251 



fellow in the median line if the ischiac margins came together, 

 as in Crocodiles ; and the prepubis would then have the posi- 

 tion of the bone in Crocodiles which most authors identify as 



Fig. 12. 



prepubis. 



¥is. 13. 



prepubis. 



ischium. 



Fig. 12. — Eestored Ventral Aspect of Pelvis of Cycnorhamphus Fraasii. 

 Fig. 13. — Restored Ventral Aspect of Pelvis of Dimorphodon macronyx. 



the pubis, but which I have supposed to be the prepubic 

 bone. I have stated the reasons for that identification 

 already * ; but if a pelvis like that of the Alligator (fig. 14) is 

 compared with that of an Ornithosaur, say Cycnorhamphus, in 

 which the shape of the ischium can be seen, it will be found 

 that the two bones are very similar in form — as similar as are 

 the prepubes. In many Ornithosaurs, such as Pt. dubius, the 

 connexion between the ischium and pubis is a narrow process. 

 If then the pubis dwindles away till the prepubis completely 

 takes its place, except that it never enters the acetabular cup, 

 we have the change which would convert the pelvis of an 

 Ornithosaur into that of a Crocodile. Thus we may accept 



* Proc. Roy. Soc. vol. xliii. p. 237. 



