Agate Mactra View fullsize Learn More About Viewing Our 3D Images (3”) .75 cmMactra achatina (Holten, 1802).Indo-Pacific.Shallow water to 50 m; common.Syn.: ornata Gray; maculosa Lamarck. Learn to read shell descriptions Kingdom: AnimaliaPhylum: MolluscaClass: BivalviaSublcass: AutobranchiaOrder: VeneridaFamily: MactridaeGenus: MactraSpecies: Mactra achatina