EXPLANATION OF PLATE V. 



Spondylus inornatus Whitf. (p. 34). 



Figs. 1, 2. Views of the outer and inuer faces of the only specimen observed. 



Plicatula densata Conrad (p. 35). 



Figs. 3, 4, 5. Views of the exterior of three different specimens, showing variations in form and surface. 

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

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



Lithophaga subalveata Conrad (p. 40). 



Fig. 9. Copy of Mr. Conrad's original figure, no specimen of it being found in any of the collec- 



tions examined. 



Mytiloconcha incrassata Conrad (p. 38). 



Figs. 10, 11. Views of the apices of two fragments of shells, all that usually remains of the specimens. 



Perna torta Say (p* 36). 



Fig. 12. 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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