CYCLADiE. 283 



Var. 1. Shell ovate, trigonal, very ventricose, 

 blackish or ochraceous ; the edge very blunt. 



Cyclas obtusalis. Nilson, 101. 



obtusale/3. Jenyjis, 1. c. 13. 



Inhab. small splashy pools and other stagnant 

 waters. 



Animal white ; siphons short, obconic ; foot very 

 extensile. 



Mr. Jenyns observes, " It is by far the most active 

 and lively species that I am acquainted with, being 

 always in motion, and residing less at the bottom than 

 the rest of the family." 



116. 2. Pisidium nitidum. Shining Pera. (t. 12. f.150.) 

 Shell orbiculate, oval, very shining, finely striated; 

 umbones rather blunt, with a few deeper striae. 

 Pisidium nitidum. Jenyns, Monog. 16. t. 20. f. 



7,8. 

 Inhab. clear water, Cambridgeshire, Battersea 

 Fields. 



Animal white ; siphon short, funnel-shaped, with a 

 spreading mouth, and a more or less plaited crenated 

 edge. 



This shell may easily be distinguished by the 

 deeper grooves on the umbo, which are more easily 

 seen in the living specimens. 



117.3. Pisidium pusillum. Minute Pera. (t. 1. f. 7.) 

 Shell orbicular, ovate, rather compressed, very 

 finely striated, scarcely inequilateral; umbones 

 rather prominent. 



Tellina pusilla. Turton, C. Diet. 167. 



Cyclas pusilla. Turton, Biv. 251. t. 11. f. 16, 17., 

 Man. ed. 1. 16. f. 7. 



