| Diagnosis |
Shell equivalve, thick and inflated, very inequilateral, posteriorly expanded. Shape somewhat irregular, elongate rectangular in outline, with strongly protruding umbones anteriorly and a broad rounded keel from umbones to posteroventral margin. Posterior margin obliquely truncate, ventral margin slightly sinuous with a well-developed byssal gape. Cardinal area wide and riblets crossed by irregular growth marks, and a few larger radial ribs on posterodorsal slope. Periostracum coarsely pilose, mainly persisting towards shell margins. Hinge straight very long and narrow. Internal margins smooth. Colour: Outside of shell often encrusted with marine growths; posterior half dark brown, anterior half creamy white with zebra-like brown stripes. Inner side more or less strongly tinged with dark brown. |