''Calliostoma ornatum'',

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

the ornate topshell, is a species of

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk in the family Calliostomatidae.

Description

The height of the shell attains 20 mm. The ornate topshell is conical shaped. It is imperforate, rather solid but not thick. It may be brown, orange-red or a brilliant violet or pale yellowish, with radiating brown flames above. The base of the shell is dotted with brown and whitish. The sculpture though variable is characteristic. The surface of

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral ...

s is encircled by spiral lirae uneven in size, and cut into very close compressed granules. There are about 10 such lirae on the penultimate whorl, but the number is variable owing to the greater or less development of interstitial riblets. The base has 10-13 concentric riblets, which have a tendency to split or become double. They are wider than the interstitial furrows. The conical spire is elevated. The apex acute. The sutures are slightly impressed. The seven whorls are slightly convex. There are generally two or three stronger lirae near the middle or periphery, and this gives at times a slightly bicarinate outline to the

body whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

. The flattened base is a little convex. The aperture is subrhomboidal and smooth inside. The arcuate columella is often bounded by a purple streak.Tryon (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
/ref> The foot is orange and there are distinct black eye spots at the base of paired tentacles.Branch, G.M., Branch, M.L, Griffiths, C.L. and Beckley, L.E. 2010. ''Two Oceans: a guide to the marine life of southern Africa''

Distribution

This snail is found only from the Cape Peninsula to Port Alfred along the South African coast from the low intertidal to at least 35m under water. It is endemic to this region.Jones, Georgina. ''A field guide to the marine animals of the Cape Peninsula.'' SURG, Cape Town, 2008.

References

* Kilburn, R.N. (1974) ''Taxonomic notes on South African marine Mollusca (3): Gastropoda: Prosobranchia, with descriptions of new taxa of Naticidae, Fasciolariidae, Magilidae, Volutomitridae and Turridae''. Annals of the Natal Museum, 22, 187–220 * Kilburn, R.N. & Rippey, E. (1982) ''Sea Shells of Southern Africa''. Macmillan South Africa, Johannesburg, xi + 249 pp. page(s): 39

External links

Branch, G.M. et al. (2002). ''Two Oceans''. 5th impression. David Philip, Cate Town & Johannesburg.
* {{DEFAULTSORT:Calliostoma ornatum ornatum Molluscs of the Indian Ocean Endemic fauna of South Africa Gastropods described in 1822 Taxa named by Jean-Baptiste Lamarck