维基百科 Viviparus, common name the river snails, is a genus of large, freshwater snails with an operculum, aquatic gastropod mollusks.[2] They are primitive members of the clade Caenogastropoda. The old name of the genus used to be Paludina. Distribution[edit] This genus is palaearctic in distribution,[3] and is known from the Jurassic to the recent periods.[4]