PALUDINA. 29 



smooth, resembling the lateral jaws of Lymnea 

 (^Moquin, t. 40. f, 5.), and advance horizon- 

 tally one against the other. Tentacles coni- 

 cal, cylindrical, blunt, and unequal; the right 

 larger, swollen at the base. Eyes on short 

 tubercles, on the outer side of the base of the 

 tentacles. Mantle simple in front ; neck with 

 a small lobe on each side. Gills single, formed 

 of three series of flat filaments, and forming an 

 oblique line down the left side of the branchial 

 cavity, and bent at the end. {3Ioquin, 76. 

 t. 40. f. 2. 12. 13.) The foot ovate, much 

 dilated, extended before the muffle, and with 

 an anterior groove. Male organ inclosed in the 

 swollen base of the right tentacle. Viviparous. 

 Shell spiral-ovate, covered with a hard olive 

 periostraca. Aperture ovate ; peristome simple. 

 Operculum ovate, annular; nucleus sublateral, 

 horny, without any shell-coat. 



1. Paludina Lam. (Marsh Shell.) 



Operculum horny, the nucleus rather on the inner 



side ; shell conoid or oblong ; mouth roundish, 



slightly angular behind ; peristome united all 



round, thin. 



They are called PaludincB from their being found 



in marshes and ditches. 



The animals are viviparous, the young being 

 hatched while the eggs are in the oviduct of the 

 mother. 



The shells of the newly-hatched individuals are 

 covered with spiral bands of cilia. 



