EXPLANATION OF PLATE II. 
OsSTREA VIRGINIANA Gmnel. (p. 27). 
Fics. 1,2. Inner and outer surfaces of a narrow form. Upper valve. — 
3,4. Similar views of a curved form of upper valve. 
5,6. Interior and profile views of a lower valve of the ordinary form. : 
7. Copy of Mr. Gabb’s figure of O. Mauricensis from vol. 4, Jour. Acad. Nat. Sci., Pl. 67. 
Ppcren MapIsontvs Say (p. 30). 
Fic. 8. View of a fragment from a large shell. 
(See other figures on Pl. Iv.) 
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