Shell thin, inflated, elongate-ovate, more than 3 times longer than high, anteriorly rounded. Umbonal reflection with small, transverse partitions. Prominent concentric ridges crossed anteriorly by strong radial ribs, the intersections bearing short spines. Half of the valves posteriorly and dorsally smoothish, densely covered with tiny granulations. Three accessory plates along the dorsal margins of the valves; anterior one roughly trigonal and elongated, median one small and transverse, posterior one long and narrow. Pallial sinus deep, broad. Inner surface with long, narrow, spatulate apophysis under the beak. Colour: dirty white; interior milky-white and porcelaneous.