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It inhabits slow rivers, canals, and ponds as far north 

 as Lancashire and Yorkshire. It is often found coated 

 with confervoid, which can easily be removed by hot 

 water and soap applied with a soft nail-brush. Both 

 this and the following species are viviparous. 



2. P. VIVIPARA (producing young alive). 



Conical, but more oval than last species. Not so glossy 

 as P. contecta ; lighter in colour, and more solid. Whorls 

 six and a half ; suture not so deep as P. contecta; umbilicus 

 none ; operculum moderately thick. 



With the exception of one locality in Scotland (near 

 Moray Firth) this species is found within the same 

 limits as P. contecta. The two species may be dis- 

 tinguished by the following characteristics : 



P. CONTECTA. 



Conical. 

 Rather glossy. 

 Dark green. 

 Suture very deep. 

 Umbilicus distinct. 

 Texture thin. 

 Apex sharp. 



P. VIVIPAKA. 

 More oval. 

 Not so glossy. 

 Light greenish yellow. 

 Not so deep. 

 Umbilicus none. 

 More solid. 

 Apex blunt. 



Var. I. unicolor. Without bands. 

 Var. II. atro-purpurea. With dark purple mark- 

 ings. 



