6 sphj]:rud^. 



straw-colour. C. flavescens, Macgillivray, Moll. Aberd. p. 246. 

 S. citrinum, l^ormand, Coup d'oeil CycL p. 1. 



Var. 2. nucleus. Smaller and much more globular. C. nu- 

 cleus, Studer, Kurz. Verzeichn. p. 93. 



Var. 3. Scaldiana. Shell more oval and of a paler colour. 

 C. Scaldiana, Norm. Cycl. p. 5, f. 1, 2. 



Yar. 4. Pisidioides. Shell subtriangular, and rather more 

 produced at its posterior slope ; ti^ansverse (or concentric) striae 

 coarser : ligament slightly perceptible on the outside. S. Pisi- 

 dioides, Gray in Ann. & Mag. Nat. Hist. July 1856, p. 25. 



Habitat : Slow rivers, lakes,, ponds and ditches, as 

 well as open drains in woods, everywhere in this country ; 

 and it occiu's in a fossil state in the upper tertiary de- 

 posits at Copford in Essex and other places. Var. 1. is 

 from Cumberland (Gilbertson) ; Westmoreland (Glover); 

 Grand Canal, Dublin (Warren) ; Aberdeenshire (Mac- 

 gillivray & Taylor) ; in a lake near Lerwick (Norman) . 

 Var. 2. Crymlyn bog, near Swansea (J. G. J.) ; Barton 

 run, Norfolk (Gunn) ; Richmond (Choules). Var. 3. 

 Oxwich marsh, near Swansea, and Thames at Clifden 

 Hampden (J. G. J.) . The colour of the body in this variety 

 is yellowish- white; tubes close together, irregularly jagged 

 at their edges, but not fringed, the branchial tube bein": 

 double the breadth of the other, which is funnel-shaped ; 

 foot white and broad. Var. 4. Grand Junction Canal at 

 Paddington. The shells of this remarkable variety are 

 much eroded, probably on account of the water being 

 charged with the refuse from manufactories or sewers. 

 The result of a careful comparison of these shells ^Yith. 

 other varieties and the typical form, and the circum- 

 stance that no other form of this variable species has 

 been found associated with it, incline me to believe that 

 it has not sufficient claims to rank as a distinct species. 

 It closely resembles the Cyclas rivalis of Dupuy (Hist, 

 nat. Moll. terr. et fluv. France, p. 668, tab. 29. f. 5), 



