26 PALUDINID&. 



ably ; in the male the right tentacle is rather shorter, and thicker 

 at the tip, than the left ; eyes moderately large, round, black ; 

 foot with a yellowish margin, broadly rounded in front, tail 

 nearly covered by the operculum. 



Shell conical, not very solid, moderately glossy, greenish, 

 sometimes tinged with brown ; with fine, close-set but irregular 

 striae in the line of growth, which are intersected by numerous 

 faint spiral lines ; body whorl with 3 and the two preceding 

 whorls with 2 broadish, brown, spiral bands ; epidermis not 

 very thick ; whorls, 6-7, very much swollen, body whorl occupy- 

 ing about half of the length of the shell ; suture exceedingly 

 deep ; mouth oval inclining to circular ; outer lip sharp, slightly 

 reflected ; inner lip forming with the other a complete peri- 

 stome ; umbilicus oblique, narrow but deep ; operculum rather 

 thin, distinctly marked with the lines of growth as well as with 

 fine, close-set, intermediate striae, nucleus depressed. 



Inhabits sluggish streams, lakes, ponds, and canals 

 as far north as Yorkshire, but it is a local species. 

 It is sluggish and irritable, and falls the instant it is 

 touched, from stones or other hard substances to 

 which it frequently attaches itself. The shell is carried 

 almost horizontally when the animal is crawling. 



Var. mrescens. Shell "bandless and of a pale greenish colour. 

 Brigg, Lincolnshire (Mr. Thos. Ball). The fry are easily distin- 

 guishable from those of P. vivipara? B.C., Supplement, vol. v. 

 p. 151. 



2. P. VIVI'PARA.* PL. IV. AND IX. 



Body dark slate-colour or nearly black, with fine yellow spots, 

 somewhat paler in colour and more distinctly spotted under- 

 neath ; tentacles bluish-black with golden-coloured spots, some- 

 what conical, rather slender ; in the male the right tentacle is 

 considerably shorter and thicker than the left ; eyes rather 

 prominent, round, black ; foot very broad, slightly truncate in 

 front, tail broad but ending in a fine point. 



Shell conical, but longer and more oval than that of the last 



* Producing its offspring alive and perfect. 



