''Vexillum semicostatum'', common name the half-ribbed mitre, is a species of small

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 ...

, 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

Costellariidae Costellariidae sometimes called the "ribbed miters" is a taxonomic family of minute to medium-sized predatory sea snails, marine gastropod mollusks. This family of snails is also sometimes referred to as ''Vexillum'' miters. The main family ...

, the ribbed miters.MolluscaBase eds. (2023). MolluscaBase. Vexillum semicostatum (Anton, 1838). Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=758950 on 2023-05-10

Description

The shell size varies between 10 mm and 22 mm The shell is ovate. The

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 of the spire are obtusely plicately ribbed. 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 ...

is smooth. The shell is chestnut-brown, the spire partially white. The columella is four-plaited. Reeve, L. A. (1844-1845). Monograph of the genus Mitra. In: Conchologia Iconica, or, illustrations of the shells of molluscous animals, vol. 2, pl. 1-39 and unpaginated text. L. Reeve & Co., London.

Distribution

This species occurs in the Red Sea, the Indian Ocean off the Mascarene Basin, Madagascar and in the Pacific Ocean off Queensland, Australia and Papua New Guinea.

References

* Anton, H.E. 1838. Verzeichniss der Conchylien welche sich in der Sammlung von Hermann Eduard Anton befinden. Halle : Eduard Anton xvi + 110 pp. * Schepman, M.M. 1911. The Prosobranchia of the Siboga Expedition. Part 4: Rhachiglossa. pp. 247-364, pls 18-24 in Weber, M. (ed.). Siboga Expeditie. Monograph 49. * Wilson, B. 1994. Australian marine shells. Prosobranch gastropods. Kallaroo, WA : Odyssey Publishing Vol. 2 370 pp. W.O.Cernohorsky, The Mitridae of Fiji - The Veliger v. 8 (1965-1966)
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