Clio pyramidata Linnaeus, 1767 forma sulcata (Pfeffer, 1879)
Shell transparent, triangular in outline, lateral sides not gutter shaped. Cross-section near apex circular, triangular near aperture. Slight dorsal curvature present. A pronounced curving of shell top to left is common. Ventral side with one rib, dorso-lateral sides with five large longitudinal ribs, sometimes seven. Transverse striation regular, conspicuous growth lines present. Embryonic shell droplet-shaped, pointed, separated from adult shell only by faint but evident constriction. Shell length: 20 mm, width: 10 mm.