1887.] 



On the Os Pubis in Crocodilia. 



23y 



pubis were not developed, the homology would be supported by a 

 ^similar plan of pelvic construction. 



Finally, there is some evidence that a similar structure is developed 

 in the abdominal region of the allies of Iguanodon, without being 

 in direct union with the pelvis. As lonor since as 1841 Dr. 

 Mantell, F.R.S., figured in the 1 Philosophical Transactions' (PI. 8, 

 fig. 2) an undetermined Wealden bone, which is now in the British 

 Museum, registered as No. 2218. It is not quite perfect, but is sug- 

 gestively similar to the pre-pubic bones of Ornithosaurs. A thick 

 sutural surface shows that it met a similar bone in the median line. 

 Subsequently Mr. S. H. Beckles, F.R.S., obtained another specimen 

 into which two such bones entered as constituents, which was exhi- 

 bited during the British Association Meeting at Brighton, in 1872, 

 and ultimately described and figured by Mr. J. W. Hulke, F.R.S.* 



Bones, like that figured by Mantell, have long been in the British 

 Museum. And Professor Cope has figured a pair of similar bones in 

 Diclonius mirabilis.f Mr. Hulke interpreted Mr. Beckles' specimen 

 as consisting of the clavicles and interclavicie. Mr. W. Davies, F.Gr.S., 

 had interpreted the isolated bones like MantelPs No. 2218, as clavicles, 

 and his determination had been accepted by Professor 0. C. Marsh ; 

 so that until M. Dollo regarded them as parts of tbe sternum they 

 had been regarded as clavicles. Dr. George Baur, of Tale College, sub- 

 sequently in 1885f suggested that the supposed sternal apparatus of 

 Iguanodon should be turned round, so that the supposed clavicles 

 would become posterior processes of the sternum, and this view has 

 been supported by Cope and adopted by myself. I suppose that the 

 interpretation of the Beckles specimen was a consequence of its con- 

 dition of preservation, by which fractures came to simulate sutures. 

 Those fractures which are assumed to limit the clavicles, so as to 

 allow the supposed interclavicie to extend between them, follow very 

 different courses from the natural limits of the bones. If Mautell's 

 fossil already referred to is superimposed upon Mr. Beckles' spe- 

 cimen, then it is manifest that the broad part of the specimen is made 

 up of two such bones which meet by median suture, and extend for 

 two- thirds the length of the specimen. Some trace of the trans- 

 verse suture may perhaps be seen which separates these bones from a 

 thin ossification which extends beyond them. Hence there can be no 

 interclavicie between the supposed clavicles ; and the evidence for the 

 identification of the clavicles disappears. Turning the specimen 

 so that the supposed clavicles point posteriorly, they will be found 

 to make a remarkable approximation in form to the pre-pubic 



* ' Geol. Soc. Quart. Journ.,* vol. 41, 1885, PI. XIY, p. 473. 

 f ' American Naturalist,' Feb. 1886, p. 154. 

 X 1 Zoologischer Anyeiger,' No. 205, p. 561. 



