Purple-ring topsnail

Description

Calliostoma annulatum, also known as the purple-ring topsnail, blue-ring topsnail or jeweled topsnail, is a medium-sized sea snail with gills and an operculum. This is a sublittoral marine gastropod mollusk in the family Calliostomatidae. This snail lives off of the Pacific coast of North America. This top shell can be found in the littoral zone from Isla San Geronimo, Baja California, north to Forrester Island, Alaska. The shell height varies between 16 mm and 35 mm. The elevated-conic shell is imperforate and rather thin. This species is distinguished by its brilliantly colored shell, which is lustrous with a gold field, dotted with brown on the spiral rows of grains, the periphery or lower edge of each whorl encircled by a zone of violet or magenta stripes, the axis surrounded by a tract of the same. The brilliance of the colors fades somewhat once the animal dies. The thin shell shows numerous granulose spiral riblets, about 7 on the penultimate whorl, 9 or 10 on the base. It has few or none interstitial lirulae. The acute, reddish apex is minute. The sutures are slightly impressed. There are about 9 whorls, slightly convex, the last angular at periphery, flattened beneath. The rhomboidal aperture is oblique, fluted within. There is no umbilicus. The head and foot of the animal has a yellow-orange color with brown spots. The color of the shell is gold with purple stripes. This species is fairly omnivorous, feeding seasonally on kelp, sessile fauna like bryozoans, and detritus. Calliostoma is a genus of small to medium-sized sea snails with gills and an operculum, marine gastropod molluscs within the family Calliostomatidae, the Calliostoma top snails (according to the taxonomy of Gastropoda by Bouchet & Rocroi (2005)). Previously this genus was placed within the family Trochidae. Calliostoma is the type genus of the family Calliostomatidae. The name of this genus is derived from the Greek words kallos (beautiful) and stoma (mouth), referring to the pearly aperture of the shell. The genus Calliostoma is known in fossil records from the Upper Cretaceous onwards. The distribution of this genus is worldwide, found mainly on hard substrates, although Japanese species have been found on sandy bottoms. These snails occur from shallow waters to bathyal depths.