Valve small, nearly square in outline, solid, considerably inflated, very inequilateral. Colour various, chocolate, chrome-yellow, pink or purple, usually a monochrome but sometimes with an occasional dark spot. Epidermis not prominently developed, presenting a lustrous surface. Sculpture: from beneath the pro-toconch radiate about eighteen round ribs which strongly denticulate the margin and are divided by flat and broader interspaces. These ribs are largest medially and continue in force to the anterior margin, but on the posterior slope they rapidly degenerate and disappear. Concentrically the furrows are latticed by about twenty-five crossbars connected across the ribs by a hooded scale.
Prodissoconch with a narrow rim, interior tumid with a central depression. No proper hinge-teeth are developed; their functions are probably discharged by about seventeen strong interlocking pits and tubercles, set without regard to the external sculpture around the broad inner margin of the valve. A wide chondrophore lies obliquely between a short anterior and a long posterior row of crenulations. Height 1,5 mm.; length 1,54 mm.; depth of conjoined valves 0,96 mm.

C. scabra resembles C. tatei, from which, without a full series, I should not have ventured to separate it. A dense enveloping epidermis conceals the shell of C. tatei in life, but C. scabra is naked. Apart from the epidermis, I rely on the more numerous radials of C. scabra to distinguish it. The northern species is besides smaller, less inflated, more square in outline, and its anterior side less developed.