Fragile Atlantic Mactra View fullsize View fullsize View fullsize Learn More About Viewing Our 3D Images (2.5”) 6 cmMactra fragilis (Gmelin, 1791).Southeast United States to Brazil.Shallow water to 10 m; common. Learn to read shell descriptions Kingdom: AnimaliaPhylum: MolluscaClass: BivalviaSublcass: AutobranchiaOrder: VeneridaFamily: MactridaeGenus: MactraSpecies: Mactra fragilis