Bull. U. vS. B. F., 1919-20. 



Plate V. 



Fig. I. — Rear view of yellow sand-shell in natural position 

 in bottom under water, showing the two siphonal open- 

 ings, the gaping shell, and the apposed margins of the 

 mantle. 



Fig. 2. — Rear view of Anodonta corpulcnta showing 

 siphonal openings. Note the very smooth margins of 

 the upper exhaleut opening and the fimbriae or "feel- 

 ers" protecting the lower or inhalent opening. 



Fig. 



-Tracks of yunng mussels in crate. 



Change in the cnnditious uf tlie water had caused them to wander mure than 

 normally. 



