230 BRITISH MOLLUSKS. 



Most observers have had their attention arrested by the sub- 

 globular ventricose proportions of this species, with its obtusely- 

 swollen umboes, though some have considered it to be a variety of 

 T. pusillum, G-melin (C.fontinalis, Drap.). Mr. Jeffreys takes this 

 view of the case, yet he describes it as being distinguished by more 

 active habits, and, in his latest work, as occurring in similar situa- 

 tions with the typical P. pusillum ; which is more conclusive of its 

 distinctness than his previous statement (Ann. Nat. Hist. 3rd series, 

 vol. iii. p. 37), that he never met with it in company with the 

 typical form. It might, in that case, be a local variety. But the 

 truth appears to be, that it is distributed generally throughout 

 Europe, and Dr. Baudon is of opinion that Mr. Temple Prime's 

 North American P. ventricosum is the same species. 



3. Pisidium pusillum. Little Pisidium. 



Shell ; obliquely orbicularly oval, rather ventricose, cinereous-olive, 

 but little glossy, moderately concentricaUy striated, 

 striae irregular, inequilateral, both sides rounded, 

 the anterior rather obliquely produced; umboes 

 moderately tumid. 

 Tellina pusilla, Gmelin (1788), Syst. Nat. p. 3231. 

 Cyclas fontinalis, Draparnaud (1801), Tail. Moll. p. 105. 

 Pisidium fontinale, C. Pfeiffer (1821), Deutsch. Moll. vol. i. 



p. 125. pi. t. f. 15, 16. 

 Cyclas pusilla, Turton (1822), Conch. Brit. p. 251. pi. xi. 



f. 16, 17. 

 Pisidium pusillum, Jenyns (1833), Trans. Phil. Soc. Cami. vol. iv. p. 302. 



pi. xx. f. 4 to 6. 

 Sab. Northern and Central Europe. Siberia. Throughout Britain. (In 

 ponds or among wet moss.) 

 In this species, the valves are less ventricose, and more strongly 

 concentrically striated than in the preceding species, and the 

 umboes are less tumid. Mr. Thompson, than whom we have had 

 no more accurate observer of the specific characters and habits 

 of the land and freshwater mollusks, says that in Ireland P. pusil- 

 lum is the most common of the genus, and distributed universally. 

 "It is generally to be met with," he says, "in ponds, drains, etc., 

 but in marshy spots, both in this country and in Scotland, I Lave 



