EXPLANATION OF PLATE V. 



SFONDVLrs INOKNATU8 Wllitf. (p. 34). 

 Kics. 1.2. View.s iil'thi) oiiter aud inner faces of the only specimen observed. 



Pl.lCATULA DKNSATA CoUI'atl (p. 35). 



PiG.s. 3, 4, 5. Views of tlie exterior of tliree different specimens, showing variations in form and surface. 

 C. Profile view of the specimen shown in fig. 5. 

 7, 8. Interiors of a lower and an upper valve. 



LiTHoPHAGA 8UBALVEATA Conrad (p. 40). 



Km. ;t. (^'opy of Mr. Conrad's original figure, no specimen of it being found in any of the collec- 



tions examined. 



Mvili.ofoNt'HA INCKAS.SATA Courad (p. 3H). 



Ku;s. HI, 11. Views of the apices of two fragments of shells, all that usually remains of the specimens. 



Perna torta Say (p. 36). 



Flu. I'J. View of the inner surface of a very heavy thickened fragment, the largest piece of the 



species found. 

 13. A cast of a small entire specimen, showing the complete form. 



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