Our British Snails 59 



below, which also shows above L. [Ancylus) 

 fluviatilis. 



Pahidina {Vivipara) contecta. — Shell dark green 

 with darker bands. Conical. Suture very deep. 

 Operculum horny. Viviparous. Local. 



Paludtna (Vivipara) vivipara. — More common 

 than contecta. Shell more oval, not so glossy, 

 light greenish yellow, suture not so deep, no 

 umbilicus, apex blunt. 



Neritina and Ancylus. 



Paludina (Bythinia) tentaculata. — (The eyes in 

 this. genus are not on foot-stalks ; the operculum 

 is shelly instead of horny). Common in slow 

 water and ditches. Shell semi-transparent, yel- 

 lowish, mouth oval, angulated above. Operculum 

 made of plates rising one above another formed 

 at different stages of growth. 



Paludina {Bythinia) leachii. — Much smaller and 

 less common than the last. Distinct umbilicus ; 

 mouth almost circular. 



Paludina (Paludestrina) ventrosa. — A brackish- 



