These shells are distinguished from tritons by a gutterlike canal or a slit-sided tube, which cuts through the edge of the aperture at its rear end. Some are of moderate size, others very large. They assume many shapes; some are squat and coarsely ornamented with thick ribs, knobs, and warty lumps, giving them the name frog shells. Others are tall and lightly ornamented. A few species are laterally compressed; some have spines, most have varices. The operculum is corneous. Most live on sand and coral rubble.