266 PI8IDIAM3. 



122. 3. PISIDIUM pusillum. Minute Pera. Shell 



orbicular, ovate, rather compressed, very 

 finely striated, scarcely inequilateral; urn- 

 bones rather prominent, acute, (t. 1. f. 7.) 



Tellina pusilla. Turton, C. Diet 167. Cyclas pusilla. 

 Turton, Biv. 251. t. 11. f. 16, 17., Man. ed. 1. 16. f. 7. 

 Cyclas fontinalis. Nilson, 101.; Drop. 130. t. 10. f. 8. 11. 

 Cyclas gibba. Alder, Cat. 41. Euglesia Henslowiana. 

 Leach, MSS. Brit. Mus., Syn. Moll. 291. Pisidium pusil- 

 lum. Jenyns, Mono*. 14. t. 20. f. 4. 6. ; Moq. Tand. M. 

 F. ii. 587. t. 52. f. 3842. ; Forbes and Hanley, B. M. 

 ii. 123. t. 37. f. 11., t. O. f. 9. Pisidium fontinale. Pfeiffer, 

 D. M. i. 125. t. 5. f. 15, 16. 



Inhab. ponds. 



b. Shell inequilateral. 



123. 4. PISIDIUM pulchellum. Beautiful Pera. - 



Shell oblique-ovate, ventricose, deeply 

 striated; umbones rather blunt, simple, 

 (t. 12. f. 151.) 



Pisidium pulchellum. Jenyns, Monog. 18. t. 21. f. 1.; Forbes 

 and Hanley, B. M. ii. 128. t. 27. f. 12, 13. Pisidium caje- 

 tanum S pulchellum. Moq. Tand. M. F. ii. 584. t. 52. f. 24. 

 28. Cardium amnicum jun. Montag. T. B. 88. 



Var. 1., smaller; shell thin, finely striated, umbones rather 

 acute. 



Pera pulchella. Leach, MSS, Cab. 'Brit. Mus., Syn. Moll. 

 292. Pisidium fontinale. Pfeiffer. Cyclas fontinalis. 

 Brown, Edin. Journ. N. and G. Soc. \. 11. t. 11. f. 5. 7.; 

 Alder, Cat. 41. Pisidium pulchellum /3. Jenyns, Mon. 

 18. t. 21. f. 2, 3. 



Var. 2., shell obliquely oval, finely striated, compressed ; mar- 

 gin acute. Pisidium pulchellum y. Jenyns, Mon. 18. 



Var. 3., shell rather oblong, very ventricose, deeply striated ; 

 edge very blunt, hinge margin nearly straight. Pisidium 

 pulchellum 5. Jenyns, Mon. 18. t. 21. f. 4, 5. 



Inhab. ponds, Birkham Common, Surrey. 

 Animal white ; siphon variable, conical or elon- 

 gate, with an entire or lobed end. 



