EXPLANATION OF PLATE 1. 

 DisciNA LUGUBRis Conrad (p. 23). 



Fif; 1. Tipper valve, natural size, and profile outline. 



2. Exterior surface, enlarged. 



3. Interior, showing muscular imprints. 



OsTREA ViHGlNiANA Gmel. var. procyon, Tuom. and Holmes (p. 28). 



Figs. 4.5. Inner and outer surfaces of a lower v.alve, of the usual size and form. 

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



146 



