FOSSIL MAMMALIA. 



Mr. G. Sowerby, who has been good enough to examine the shells which were 

 found with the remains of the quadrupeds, has given me the following list. 



Voluta angulata. 



colocynthis. 



Olivet Brasiliensis. 



Nearly related to 0. patula, but 



specimen imperfect. 



Nearly related to 0. oryza ; less 



nearly to small species now liv- 

 ing at Bahia Blanca. 



Nov. spec. 



Buccinum cochlidium. 

 globulosum. 



One or two minute species, per- 



haps young specimens, — un- 

 known. 



Nov. spec. (?) same as one now 

 living in the bay. 



Nov. spec. (?) nearly related to 

 last; differs in not being granu- 

 lar on the surface. 



10. Trochus 



12. Assiminia (?) Minute species, identical with one 



living in the bay. 



13. Bulinus nucleus. 



14. Fissurella Probably same as a kind (nov. 



spec. ?) living in the bay. 



15. Crepidula muricata. 

 Nov. spec. 

 Closely related to, or identical with 



C purpurascens. 



Same as recent kind (nov. spec.) 

 living in the bay. 



Near to N. margaritacea. 



Minute species, unknown. 

 Ditto ditto 



Nov. spec. (?) very imperfect spe- 

 cimen. 



Oysters of the same size now live 

 in the bay. 



16. 



17. Cythercea 



18. Modiola 



19. Nucyla 



20. Corbula 



21. Cardita 



22. Pecten 



23. Ostrea 



I may add that a fossil encrusting coralline is the same with one now living in the bay. 



Of these shells it is almost certain that twelve species (and the coralline) are 

 absolutely identical with existing species ; and that four more are perhaps so ; 

 the doubt partly arising from the imperfect condition of the specimens. Of the 

 seven remaining ones, four are minute, and one extremely imperfect. If I had 

 not made a collection (far from perfect) of the shells now inhabiting Bahia 

 Blanca, Mr. Sowerby would not have known as living kinds, five out of the twelve 

 fossils : therefore, it is probable, if more attention had been paid to collecting the 

 small living species, some of the seven unknown ones would also have been found 

 in that state. The twelve first shells, as well as the four doubtful ones, are not 

 only existing species, but nearly all of them inhabit this same bay, on the shores 

 of which they are likewise found fossil. Moreover, at the time, I particularly 

 noticed that the proportional numbers appeared closely similar between the dif- 

 ferent kinds, — in those now cast up on the beach, and in those embedded with 

 the fossil bones. Under these circumstances, I think, we are justified (although 

 some of the shells are at present unknown to conchologists) in considering 

 the shingle strata at Punta Alta, as belonging to an extremely modern epoch. 



c 



