About Calliostoma zizyphinum (Linnaeus, 1758)
This species has a solid, regularly conical shell that is straight-sided and imperforate. The shell holds up to 12–13 whorls, and is sculptured with regular spiral grooves and ridges, crossed by fine prosocline growth lines. The apex is very small, made up of a single smooth rounded whorl. Several subsequent whorls each have 4 granose spiral ridges, which become smooth, and either obsolete or narrow on the later whorls. The body whorl has a prominent peripheral keel that bears two broad ridges; matching ridges sit above the suture on preceding whorls. The base of the shell is rather flat, and the inner lip is reflected over a shallow umbilical groove. The periphery is angular, encircled by a smooth rounded rib that forms a supra-sutural band or fasciole on the spire. The aperture is quadrate, and the cylindrical columella is nearly straight. The shell colour is variable. The ground colour can be yellowish brown, pale pink, or violet, with brown, red or purple streaks and blotches on the periphery. Blotches on the keel are generally darker, more frequent, and more regular than blotches on other parts of the shell. The upper surface of the shell is radiately clouded with brown. The base of the shell is either unicolored or obscurely radiately streaked. Pure white or violet specimens are found occasionally. This marine species is distributed in European waters from Northern Norway to the Azores, and also occurs in the Mediterranean Sea.
