''Nassarius vinctus'', common name the violet-mouthed dog-whelk, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Nassariidae The Nassariidae, Nassa mud snails (US), or dog whelks (UK) are a taxonomic family of small to medium-sized snails, mostly marine gastropod mollusks in the clade Neogastropoda. These snails have rounded shells with a high spire, an oval ap ...

, the nassa mud snails or dog whelks.

Description

The length of the shell attains 22 mm. The shell is small, with a relatively elongated

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spire ...

and weakly convex

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). In nature File:Photograph and axial plane floral diagra ...

s. The periphery is rounded, and the

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

is variable, often reticulate. It consists of low axial ribs crossed by broad, flat spiral cords with narrow intervals, though the axial ribs may be weak or absent in some specimens. The inner

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

features a thin, glossy

callus A callus (: calluses) is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, b ...

that extends over the parietal region. The outer lip is not noticeably thickened and may be smooth internally or display weak, in-running ridges. The siphonal notch is wide and shallow. Fresh specimens are reddish-brown to purplish-brown, typically featuring pale spiral bands. Axial ribs, when present, are paler. The inner lip and interior of the aperture are violet, though the color intensity fades over time. The shell is often encrusted with marine organisms, and its surface frequently becomes chalky or etched.

Distribution

This marine species is endemic to South Afriuca and occurs off the West coast and Agulhas Bank (northern Namibia to western Transkei) at depths between 10 m and 150 m.

References

* * * Marais J.P. & R.N. Kilburn (2010) ''Fasciolariidae''. pp. 106–137, in: Marais A.P. & Seccombe A.D. (eds), Identification guide to the seashells of South Africa. Volume 1. Groenkloof: Centre for Molluscan Studies. 376 pp. * *

External links

* * * * {{Taxonbar, from=Q13877463 vinctus Endemic molluscs of South Africa Gastropods described in 1877