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. {Moquin^ 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. 
