PLATE III. 



Ventral aspect of Hinges, drawn by camera lucida, of : 



1. Pisidium amnicum. 



2. astartoides. 



3. casertanum. 



4. pusillum. 



5. - personation. 



6. nitidum. 



7. siibtruncatum. 



8. pulchellum. 



9. henslowanum. 



