EXPLANATION OF PLATE I. 

 Discima lugubris Conrad (p. 23). 



Fig 1. Upper valve, natural size, and profile outline. 



2. Exterior surface, enlarged. 



3. Interior, showing muscular imprints. 



Ostrea Virginiana Gmel. var. procyon, Tuom. and Holmes (p. 28) 



Figs. 4, 5. Inner and outer surfaces of a lower valve, of the usual size and form, 

 6. Exterior of a large valve, the apical portion lost, 



146 



