PLATE XXXI. 



PAGE 



Figs. 1-5. Panopea elongata Conrad 162 



1. Left aspect of cast. Fort Washington. 



2. Left valve. Aquia Creek. 



2a. Surface of same specimen. X 17 



3. Eight valve of Fig. 1. 



4. Left valve. Fort Washington. 



5. Eight valve. Fort Washington. 



