PLANORBIS. 41 



also are rounder, and do not increase so quickly, making the 

 whole shell more compact. Found in the neighbourhood of 

 Birmingham by R. M. Lloyd, y.C, Feb. 1874, p. 7. 



C. Whorls many, keeled. 

 6. P. spiror'bis,* Muller. Pl. IV. 



Body grey, with more or less of a purplish or reddish tinge ; 

 tentacles filiform, long, finely pointed, transparent, of an ash- 

 colour very faintly tinted with pink ; eyes small, round, intensely 

 black ; foot short, slightly transparent at its edges, bluntly 

 rounded in front and ending in an obtusely angular tail. 



Shell usually somewhat concave above and flattish underneath, 

 sometimes the reverse, or slightly concave both above and 

 below ; rather thick, shining, of a brown horn-colour, with well- 

 defined close-set striae in the line of growth, and very indistinctly 

 striate spirally ; epidermis, thin ; periphery somewhat angular, 

 often obtusely keeled below ; whorls 5-6, rounded but somewhat 

 angulated, body whorl rather broader than the others ; suture 

 deep ; mouth nearly round, often provided internally with a rib ; 

 outer lip scarcely reflected ; iniier lip spread on the base of the 

 penultimate whorl, continuous with the outer lip; umbilicus 

 large but shallow. 



Inhabits stagnant water and sluggish streams in 

 every part of Great Britain. As is the case with 

 other members of the genus, the shell of this species 

 is often distorted, the whorls being drawn out and 

 separated from each other, causing it to assume the 

 appearance of a corkscrew. 



Var. ecarinata. — " Shell smaller, light grey, having one whorl 

 less than usual and no trace of a keel," B.C., vol. i. p. 87. Gwyn 

 Jeffreys says it appears to be very rare in this country, he only 

 found it once and that was in Oxwich Marsh near Swansea. My 

 friend Dr. Laver of Colchester informs me that he has met with 

 it in Essex. 



* Having a round spire. 



