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Calliostoma annulatum

Domain Eukarya
Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Prosobranchia
Order Archaeogastropoda
Superfamily Trochacea
Family Trochidae
Genus Calliostoma


Common Name: Top snail or Top shell
Conical shell usually orange-yellow, dotted with brown and with a bright purple or violet band encircling the lower edge of each whorl, with 8 or 9 whorls; body of living animal orange, with brown dorsal spots. Size to 30 mm height.

Range: Alaska south to Baja California. They occur very rarely at Race Rocks. They are more common however on the islands to the West, Church Island and the Bedfords in Beecher bay.

Habitat: on the open coast. Calliostoma annulatum reportedly moves up the kelp stipes to near the sea surface in 'bright weather' and descends under other conditions. These animals can move rapidly.

It's an omnivore. In the spring the food is mainly the kelp itself; the snail prefers animal foods when these are available especially hydroids (e.g. Obelia sertularians) and encrusting bryozoans (Membranipora; Hippothoa), Detritus and some diatoms and copepods are taken, too.On the sea floor, they take some of the cnidarian Corynactis californica and scavenge on dead fish. In aquaria, the snails have been seen to eat hydroids, the anemone Epiactis prolifera, the stalked jellyfish Haliclystis, dead nudibranchs (Polycera atra), dead keyhole limpets (Fissurella volcano), dead chitons, nudibranchs eggs, and other items, including even canned dog food. Although jaws are often poorly developed in the Trochidae, observations by Paron (1975) suggest that they play an important role here. Hydroids stems in the gut often appeared 'neatly cut into short segments'. Further when attacking anemones, Calliostoma annulatum after initial contact, 'would rear up on its metapodium, expand its lips, and suddenly lunge forward while bitting at one of the anemone's tentacles. A dorid nudibranch was also attacked in this way.

The shell bears a layer of mucus which makes it slippery and not easily held by potential predators.

Reproduction: Males usually spawn first. Green eggs, each in clear envelopess and a gelatinous coat thick, are shed in a soft gelatinous coating. In the San Juan Archipelago, specimens collected June-August may spawn if placed in sea water at 18-22 C


  1. Harbo, R. 1997. Shells & Shellfish of the Pacific Northwest -A field guide.- -Pg. 75-. Harbour Publishing.
  2. Kozloff, E. N. 1996. Marine Invertebrates of the Pacific Coastfic Northwest. -Pg. 203-. University of Washington.
  3. Morris, R.H., Abbott, D, and Haderlie. 1980. Intertididal Invertebrates of California. -Pg. 250-. Stanford University Press, Stanford California.
  4. Strathmann, M. 1987. Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast. Data and Methods for the Study of Eggs, Embryos, and Larvae. -Pg. 233-234-. University of Washington Press.
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The Race Rocks Taxonomy
This file is provided as part of a collaborative effort by the students of Lester B. Pearson College
Feb. 2002 Maria Belen Seara PC yr 28
Lester B. Pearson College