''Exomilus dyscritos'' 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

Raphitomidae Raphitomidae is a family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families". ''Malacologia'' 47(1-2). . 39 ...

Description

The length of the shell attains 9.1 mm, its diameter 2.7 mm. (Oriignal description) The solid, white shell is long and narrow. A co-type shows a brown tinting of the two carinae and of that part of the axial ribs connecting them, most marked at the tubercles of junction. It contains seven

whorls 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 d ...

. The

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...

contains two , homostrophe, convex whorls with 20 fine spiral incisions ending abruptly in a

varix A varix (pl. varices) is an abnormally dilated vessel with a tortuous course. Varices usually occur in the venous system, but may also occur in arterial or lymphatic vessels. Examples of varices include: * Varicose veins, large tortuous veins usua ...

. The spire whorls show angulation at one-fourth the distance from the lower suture. They are uniformly concave between the angulations. Their sculpture shows axial ribs, valid, rounded nearly as wide as the interspaces, and spiral lirae, wider anteriorly, wider than their interspaces, crossing the ribs. There are six above the angulation, and two below it. Fine accremental striae can be seen under the lens. The suture is distinct, linear, undulating, convex between the ribs. 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 oblong with two median rounded carinae, the upper larger, more prominent, forming the angulation (in the spire whorls), the lower producing the upper margin of the suture, tuberculated by the axial ribs, which cease at the lower one. Six spiral lirae above them, two between them, and ten of varying size below them on the concave base. Aperture subtriangular, outer side straight, inner sigmoid. Outer lip thin, slightly excavated just below the suture for one-sixth of its extent to form a shallow sulcus, with a margin feebly thickened and everted, then excavated again to the upper carina, an acute short projection between the two excavations. The edge is crenulated by spiral lirae and carinae. The outer lip begins at the lower carina and is concavo-convex to the anterior notch. The columella is concavo-convex from behind forwards. Verco, J.C. 1906. Notes on South Australian marine Mollusca with descriptions of new species. Part III. Transactions of the Royal Society of South Australia 30

Distribution

This marine species is endemic to

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and occurs off South Australia and Tasmania

References

* Hedley, C. & May, W.L. 1908. Mollusca from one hundred fathoms, seven miles off Cape Pillar, Tasmania. Records of the Australian Museum 7: 108-125, pls 22-25

External links

*
Hedley, C. 1922. A revision of the Australian Turridae. Records of the Australian Museum 13(6): 213-359, pls 42-56
{{DEFAULTSORT:Exomilus Dyscritos dyscritos Gastropods described in 1906 Gastropods of Australia