| Diagnosis |
Shell rather thin and small, subquadrate in outline, with a short and ill-defined posterior ear which is not drawn out into a wing-like process. Anterior margin protruding only slightly or not at all beyond the tip of the anterior ear. Outer surface of shell, when not worn, covered with numerous, flattened and brittle, imbricating concentric scales bearing slender, radially projecting spines, especially toward the margins. Hinge lines with 2 small teeth on each valve; 1 rounded anterior tubercle just in front of the umbo, and 1 slightly slanting posterior ridge behind the ligamental area. Parallel accessory ridges sometimes developed on both valves, so that the posterior teeth appear double. Colour: outside of shell with a variable coloration, usually white to tan with a number of purple, or brown to black radiating bands and sometimes a superimposed pattern of finely wavy concentric lines of reddish brown. Internal nacreous area with pale yellow to deep orange-gold tint. Non-nacreous margin with white porcelaneous patches, generally alternating with irregular, dark purplish brown or black blotches. |