The Collaborative International Dictionary of English v.0.48:

Paludina \Pal`u*di"na\, n.; pl. L. Paludin[ae], E.
   Paludinas. [NL., fr. L. palus, -udis, a marsh, pool.]
   (Zool.)
   Any one of numerous species of freshwater pectinibranchiate
   mollusks, belonging to Paludina, Melantho, and allied
   genera. They have an operculated shell which is usually
   green, often with brown bands. See Illust. of Pond snail,
   under Pond.
   [1913 Webster]