the typical sculpture tiled, with nodules, that makes easy to recognize it from its congenerous ones, is well defined starting from its juvenile stage.
Even its outline does not undergo sensible variations in the different growth stages. The average length is 7-8 mm.
Always uniform dirty white in colour.

Arca imbricata Bruguière, 1789 Mossy Ark Distribution: North Carolina to Texas; West Indies; Brazil; Bermuda. Size: 38 to 63 mm (1 1/2 to 2 ½ in). Description: Color light brown to whitish at umbones, interior whitish-purple; shape elongate-rectangular with posterior end broader; sculpture of radial ribs crossed by commarginal growth lines, giving beaded, cancellate appearance; a sturdy ridge or sulcus extends from umbo to posterior margin; hinge line long, nar- row, and straight with numerous erect teeth that become smaller toward the center. Habitat: Byssally attached to hard substrates; epifaunal. Found at depths from shoreline to 64 m (210 ft). Remarks: Live at SPI and on artificial reefs of Texas. See Andrews (1977); Odé (1978a).

Habitat: common in the coralligenous colonies {Cladocora) and in the concretions of calcareous algae. Distribution: never common all over the Mediterranean. Italy.