Atlantic Ribbed Mussel View fullsize Learn More About Viewing Our 3D Images (3”) 7.5 cmGeukensia demissa (Dillwyn, 1817).East Canada to Florida; introduced to Calif. Peat marshes.Common.Syn.: plicatulus Lamarck. Learn to read shell descriptions Kingdom: AnimaliaPhylum: MolluscaClass: BivalviaOrder: MytilidaFamily: MytilidaeGenus: GeukensiaSpecies: G. demissa