Shell thin, translucent, small, shaped like an axehead, with no gape, very inequilateral. Posteriorly the shell is truncate for almost the whole height, the truncated portion being sharply and deeply infolded. A curve of half a circle is approximately described by the ventral and anterior margin. Colour, pale brown. Sculpture : the whole surface is evenly covered by fine, close, radiating riblets, which are microscopically beaded, diverge from a median parting and are occasionally disjointed by concentric growth lines. Cardinal area triangular, overhung by the incurved beak and sharply defined by a ridge above. Hinge line short. Auricles almost obsolete, cartilage narrow, in an obliquely descending, shallow sulcus, which barely undulates the hinge margin. Inside polished, faintly tinged with purple; the margins denticulated by the radiating riblets. Height, 8 mm.; length, 6 mm.; breath of conjoined valves, 4 mm. Hab.:Only known within Sydney Heads;