The shell is smaller and much more depressed than those of full-grown specimens of vulgata Linné, with, often, very marked radial ridges, and a tendency to show a posterior margin more angular than round. MarLIN notes « two capricious rays running to the edge » (the rear one); considering the present specimen, this occurrence seems to be reserved to the inner surface, where the radiating pattern is peculiarly contrasting, and restricted to the marginal area, except for two doubled rays that arise from the muscular print.