HEiLPKiN I TERTIARY. 311 



Ostrea falciformis Conrad. 

 Ainericau Journal of Conchology, I, page, 140. From Mississippi. 



Sv.v. — 0. diraricataf Lea. Snijra. 



Ostrea mortonii Gabb. 



From Alabama and South Carolina. Proceedings of the Academy 

 of Natural Sciences of Philadelphia for ISCl, page 329. 



Syx.—O. panda (pars) Morton. Synopsis Organic Evmaius, page 51. 



Ostrea seUcvformis Conrad. 



(Plate LXII, Figs. 1,2; Plate LXIII.Fig. 1.) 

 From the Eocene of Alabama, South Carolina, and Virginia. Pub- 

 Ifshcd by Conrad in his Fossil Shells of the Tertiary Formation, first 

 edition, page 27. 



SvN. — 0. radians Conrad; same work an<l page. 



Ostrea thirsw Gabb. 



(Plate LXIII, Figs. 4, 5, G.) 

 This form was published by Gabb as a Cretaceous species in the Pro- 

 ceedings of the Philadelphia Academy of Sciences for 1861, page 329; 

 hut it is now tnown that the strata from which it oomesareof Eocene age. 

 Gabb referred it to the genus Oryphesa, but, although it approaches 0. 

 vesieularis in form, I am disposed to place it under true Ostrea. 



Ostrea trigonalis Conrad. 



Proceedings of the Philadelphia Academy of Natural Sciences, VII, 

 page 259. From Mississippi. 



? Ostrea tuomcyi Conrad. 



This name is given by Conrad, No. 695 of the Smithsonian Check 

 List, as coming from Mississippi. I have seen no specimens of this 

 species, nor have I been able to discover where it is described. 



OLIGOCENE. 



Ostrea georgiana Conrad. 



Conrad published this .species in the Journal of the Philadelphia 

 Academy of Natural Sciences, VII, p. 156. It is reported as coming 

 from Georgia, South Carolina, Mississippi, and Lower California (?). 

 There is a large oyster in the collection of the Academy from Lower Cal- 

 ifornia, marked 0. georgiana; it certainly greatly resembles that species, 

 but its characters are to some extent obliterated, which prevents abso- 

 lute identification. I should not be surprised if, on comparison with 

 European specimens, the 0. georgiana will be found to be only a variety 

 of 0. crassissima Lamarck (Miocene of a very large portion of Europe). 



