FAMILY CARDIACEA. 



231 



found it in company with and adhering to the same stones as land 

 niollusca which inhabit snch places, as Vertigo palustris, etc. In 

 the north and south of Ireland, I have procured it among moss, 

 which was kept moist only by the spray of the waterfall." Nilsson, 

 the Swedish naturalist, mentions having collected living specimens 

 beneath the bark of trees fallen in damp places. It has rather a 

 northern range, passing into Siberia. 



French conchologists characterize four varieties of P. pusillum, 

 apart from two varieties of P. obtusale. Mr. Jenyns describes the 

 animal as being white, with a short entire-margined siphonal tube, 

 varying in shape from cylindrical to subconic. 



4. Pisidium nitidum. Shining Pisidium. 



Shell ; suborbicular, compressed towards the ventral margin, ventri- 

 cose towards the umboes, thin, Hght horn-colour, 

 glossy, iridescent, concentrically ridged and stri- 

 ated, with a few deep grooves near the umboes, 

 nearly equilateral, sides obliquely rounded, the 

 anterior rather produced ; umboes prominent, 

 obtuse. 

 Pisidium nitidum, Jenyns (1833), Trans. Phil. Soc. Camb. 



vol. iv. p. 304. pi. xx. f. 7, 8. 

 Cyclas nitida, Hanley (1843), Sec. Biv. Shells, p. 90. 

 Pisidium roseum, Scholtz (1843), Settles. Land und Wass. 



Moll. p. 140. 

 Pisidium incertum, Normand (1854), Coup d'ceil Ct/cl. p. 6. 

 Hab. Throughout Europe. (In stagnant waters.) 



Pisidium nitidum, though not described until it was observed in 

 the fens of Cambridgeshire and Lincolnshire in 1833, by Mr. Jenyns, 

 is common in all the stagnant waters of Europe. It is of a rather 

 less oblique form, more orbicular than other species, and it is charac- 

 terized by a pale glossy iridescent appearance ; there is also a 

 marked pecrdiarity in the presence of from three to five deep grooves 

 in the vicinity of the umboes. Mr. Jenyns notes a difference 

 in the animal which is, perhaps, of yet greater specific importance. 

 "The siphon," he says, "is short and funnel-shaped, with a patu- 

 lous aperture, of which the margin is more or less crenated or 

 plicated." 



