204 SYSTEMATIC PALEONTOLOGY 



Description. — " Shell ovate compressed, with the front margin straight, 

 and obliquely truncated toward the cartilage-slope. Hinge with the pri- 

 mary teeth 3-sides and striated Shell rather more than two 



inches long, and about three and one-half inches broad. The substance 

 is thick, the beaks decorticated, and the inside of a rose color." Dillwyn, 

 1817. 



A few specimens of this common fresh-water clam have been found 

 apparently in the same bed with the marine Pleistocene fossils at Lang- 

 leys Bluff and Wailes Bluff in southern St. Mary's County. Casts of a 

 IJnio in apparently purely fresh-water beds at Bodkin Point, Anne Arun- 

 del County, may also belong to the same species. It is not re- 

 ported from other Pleistocene localities. In the Eecent it has an exten- 

 sive range in the fresh-waters of the eastern United States. 



Width, 58 mm.; height, 35 mm. 



Occurrence. — Talbot Formation. Wailes Bluff near Cornfield Har- 

 bor; Langleys Bluff, St. Mary's County; at mouth of Back Eiver, 

 Baltimore County. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 and U. S. National Museum. 



Superfamily OSTRACEA. 

 Family OSTREIDAE. 



Genus OSTREA Lamarck. 



Ostrea virginica Grmelin. 



Plates LXI, LXII, LXIII. 



Ostrea virginiana of Lister and other nonbinomial writers. 

 Ostrea virginica Gmelin, 1792, Syst. Nat., p. 3336. 

 Ostrea fundata Holmes, 1858, Post-PL Fos. S. C, p. 11, pi. ii, fig. 10. 

 Ostrea virginica Dall, 1889, Bull. U. S. Nat. Mus., No. 37, p. 32. 

 Ostrea virginica Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, 

 p. 687. 



Description. — " 0. testa subaequivalvi crassa rudi lamellosa; valvge al- 



terius rostro prominente." Gmelin, 1792. 



The common oyster occurs in great numbers in the Marvland Pleisto- 



