Note:  Do not rely on this information. It is very old.

Paludina

Paludina, the typical genus of the family Paludinidce, one of the best known groups of pond snails; they belong to the sub-order Prosobranchiatn, and began in tipper Jurassic times. The Purbeck marble and the Petworth marble from the Wealden beds of Sussex are both made up in the main of Pahtdina shells; the latter is well known from its use for fonts.