PISIDIUM. 11 



Darlington, and North Stainley, near Ripon, &c. It is 

 generally distributed in Ireland, and several localities 

 are recorded in Scotland. 



P. PULCHELLUM. Jenijus. PL I, fig. 10. 



Shell obliquely ovate, deeply striate, inequilateral; umbones simple, 

 rather bluut. 



Pisidium fontinale. Brown. Cyclas fontinalis. Brown. 



This species varies very much both in shape and 

 size, sometimes being smaller than P. ohtusale, and 

 sometimes almost as large as P. cinereum ; but it may 

 generally be known by its deeper striae, more shining 

 appearance, and by being more inequilateral than the 

 others which have been described. On account of the 

 multiplicity of shapes which this shell assumes, many 

 varieties have been appended to the species, by most 

 conchologists, all of which seem more or less to diverge 

 into one another. Its colour varies from an ashy hue 

 to a yellowish white. 



Hah. It is one of the commonest of the smaller 

 Pisidia, being distributed generally over England, 

 Ireland, and Scotland ; inhabiting both running streams 

 and stagnant pools. 



P. Henslov^ianum. Sheppard. PI. I, fig. 11. 



Obliquely oval, finely striated, ventricose ; umbones acute, with a 

 laminar projection. 



With the exception of the laminar projection and its 

 greater ventricoseness, the description of P. pulchellum 

 would equally apply to this species. The surface is 

 generally rather glossy, of an ashy grey or yellowish 

 horn colour. The length varies from a sixth of an 

 inch to two lines and a half. 



Hob. Ditches and slowly flowing streams ; the re- 

 corded localities are few, Kiver Cam, Thames at Hen- 

 ley, Ackworth, and several places near Oxford.* 



* James Dalton, B.A., who has kindly furnished us with many 

 localities, states " it has become abundant since the introduction of 

 the American Anacharis Alsinastrum. Formerly the shell was very- 

 rare." 



