36 



The shell is turbinated, or twisted, and has a pro- 

 duced spire; the convolutions are generally rounded. 

 The aperture is more or less oval, the operculum horny, 

 and the epidermis is coloured. 



It is bisexual, and also ovo-viviporous, bringing forth 

 its young alive, and in perfectly-formed shells. 



M. Bouchard Chautereaux informs us, from bis in- 

 vestigations, that, in autumn, the females contain each 

 twenty or thirty eggs, and that the young ones are 

 brought forth when they are little more than two 

 months old. 



Paludina vivipara (Common Marsh Shell). Linncsus. 

 Figures 14 and 15. 



The present interesting shell in general form and 

 size approaches more closely to the garden snail-shell 

 than any other of the aquatic species. The umbilicus 



