Clio pyramidata Linnaeus, 1767 forma martensi (Pfeffer, 1880)
Shell transparent, elongate-triangular in outline, slightly curved ventrally. Middle part of shell convex in outline; anterior section with sharper lateral ribs, with parallel or somewhat diverging lateral sides. Poorly developed lateral ribs do not project laterally. Dorsal surface usually with five ribs, transverse striation on both surfaces distinct. Shell length: 17 mm, width: 9 mm.