EXPLANATION OF PLATE XII. 

 Dione Sayana Conrad (p. 75). 



Fig. 1. A copy of Conrad's figure of this species, nothing but fragments of the cardinal portion 

 being obtained from New Jersey, too poor for illustration. 



Mercenaria cancellata Gabb (p. 68). 



Figs. 2,3. View of the interior, the hinge imperfect, and of the exterior of the type specimen of the 

 species, none other having been obtained. 



Mercenaria plena Conrad (p. 69). 



Figs. 4,5. Exterior and interior of a right valve. 



6. Anterior profile view of the valves in conjunction. 



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