''Austrodrillia dimidiata'' 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

Horaiclavidae Horaiclavidae is a family of predatory sea snails, marine gastropod mollusks in the superfamily Conoidea. In 2011 this family was split off from the family Pseudomelatomidae (formerly the subfamily Crassispirinae McLean, 1971) by Bouchet P., Ka ...

. It was formerly included within the family

Turridae Turridae is a taxonomic family name for a number of predatory sea snails, marine gastropod mollusks in the superfamily Conoidea. MolluscaBase (2018). Turridae H. Adams & A. Adams, 1853 (1838). Accessed through: World Register of Marine Specie ...

Description

The length of the shell attains 7.9 mm, its diameter 2 mm. (Description by Joseph Verco) The solid, elongate-fusiform shell consists 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, including the blunt

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 ...

, which merges into the spire insensibly. The first whorl and a half are smooth and rather flat; the next is scarcely convex, and has at first distant invalid axial angulations, which gradually become more numerous and costulate. In the next whorl they become more distant again, and remain throughout the shell as feeble axial angulations which are just visible when looking at the shell from the apex. The spire-whorls are subconvex, subangulate just below the middle, and have the upper fourth somewhat adpressed just below the simple impressed suture. The aperture is oblique oblong-ovate. The

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...

is short, wide, scarcely notched. The outer lip is solid but sharp, with a deep round sinus separated from the ascending suture by a callus from the posterior part of the inner lip, then straightly convexly antecurrent to two shallower sinuses at the base of the siphonal canal. The inner lip shows a complete smooth thin applied glaze, thickened behind. The spiral incisions, which begin in the second half of the first sculptured protoconchal whorl, cut the surface up into flat slightly rounded ribs, increasing to eleven in the penultimate and twenty-four in 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 second below the suture and that at the angulation being the widest. Microscopic incremental striae scratch the whole surface and have the sinuosities of the outer lip. A narrow white spiral, articulated with brown, ornaments the angulation, with a fainter narrower one above, and a rather wider brown spiral articulated with white runs from the back of the aperture over the dorsum nearly to the lip margin. The general colour is brown, with darker irregular spots and clouds. Verco, J.C. 1909. ''Notes on South Australian marine Mollusca with descriptions of new species. Part XII; Transactions of the Royal Society of South Australia v. 33 (1909)
(described as ''Drillia achatina'' )

Distribution

This marine species is endemic to Australia and occurs off South Australia.

References

Sowerby, G.B. (3rd) 1897. ''List of Pleurotomidae of South Australia, with descriptions of some new species.'' Proceedings of the Malacological Society of London 2: 24–32
* Hedley, C. 1922. ''A revision of the Australian Turridae''. Records of the Australian Museum 13(6): 213–359, pls 42–56 * Wells, F.E. 1990. ''Revision of the recent Australian Turridae referred to the genera Splendrillia and Austrodrillia''. Journal of the Malacological Society of Australasia 11: 73–117 * Wilson, B. 1994. ''Australian Marine Shells.'' Prosobranch Gastropods. Kallaroo, WA : Odyssey Publishing Vol. 2 370 pp.

External links

Tucker, J.K. 2004 ''Catalog of recent and fossil turrids (Mollusca: Gastropoda)''. Zootaxa 682:1–1295
{{DEFAULTSORT:Austrodrillia Dimidiata dimidiata Gastropods of Australia