228 



BRITISH MOLLUSKS. 



The British, species of Pisidiiim are : — 



1. amnicum. Shell large, triangular, anteriorly slopingly pro- 



duced, strongly concentrically ridged. 



2. obtusale. Shell very small, suborbicularly ovate, nearly 



equilateral, moderately striated, umboes obtuse. 



3. pusillum. Shell very small, obliquely oval, anterior side 



rather produced, moderately striated, umboes tumid. 

 4s. nitidum. Shell very small, suborbicular, concentrically ridged 

 and striated, glossy, umboes obtuse. 



5. Casertanum. Shell small, triangularly orbicular, very in- 



eqiiilateral, anteriorly produced, finely striated, dull. 



6. pulchellum. Shell minute, obliquely orbicular, anteriorly 



obliquely produced, prominently striated, dull. 



7. Henslowianum. Shell minute, obliquely subtriangular, 



rhombic, finely concentrically striated, umboes calyculate. 



1. Pisidium amnicum. River Pisidium. 



Shell ; somewhat triangularly oblique, compressed, solid, cinereous 

 olive, glossy, strongly concentrically ridged 

 and grooved, anterior side slopingly produced, 

 posterior abruptly truncate ; umboes compara- 

 tively pointed. 



Tellina amnica, Miiller (1774), Verm. Hist, part ii. 

 p. 205. 



Tellina striata, Sckroter (1779), Fluss-Conch. p. 193. 



Tellina rivalis, Maton (1797), Trans. Linn. Soc.xcA. iii. 

 p. 44. pi. xiii. f. 37, 38. 



Cyclas palustris, Draparnaud (1801), Tall. Moll. p. 106. 



Cardium amnicum, Montagu (1803), Test. Brit. p. 86. 



Cyclas amnica, Fleming (1814), JRdin. Encyc. vol. vii. 

 p. 92. 



Cyclas obllqua, Lamarck (1818), Anim. sans vert. vol. v. p. 559. 



Pisidium obliquum, C. Pfeiffer (1821), Deutsch. Moll. vol. i. p. 124. pi. v. 

 f. 19, 20. 



Pisidium amnicum, Jenyns (1833), Trans. Phil. Soc. Camb. vol. iv. p. 309. 

 pi. xix. f. 2. 



Pisidium inflatum, Megerle (1838), Porr. Mai. Comasc. p. 121. pi. ii. f. 13. 



Pisidium intermedium, Gassies (1849), Desc. Pisicl. Aquit. p. 11. pi. i. f. 4. 



