''Scrinium impendens'' 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 Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Mitromorphidae Mitromorphidae is a monophyletic family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet, P. (2011). Mitromorphidae Casey, 1904. In: MolluscaBase (2018). Accessed through: World Register of Marin ...

.MolluscaBase (2018). Scrinium impendens (Verco, 1909). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=434883 on 20 April 2018

Description

The length of the shell attains 6.4 mm, its diameter 2.5 mm. (Original description) The solid, white shell contains 7

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 ...

of 2 smooth depressed convex turns. The spire-whorls are sloping, swollen above the linear somewhat undulating suture, and barely swollen below it. The base of the shell is slightly contracted. The

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

is oblong-oval, narrower behind, widely open in front, with a shallow notch. The outer lip is simple, sharp, thickened by a marked

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 ...

outside, which ascends roundly at the suture and bounds a shallow, wide posterior sinus. The profile is convex, barely sinused anteriorly. The axial ribs are roundly trigonal, sinuous, undulating the upper suture, most valid at the swelling of the whorl, half as wide as the interspaces, vanishing towards the base, and becoming obsolete towards the aperture. There are very crowded spiral incisions all over, and still finer sinuous axial growth scratches, finely granulating the surface. 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)
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Distribution

This marine species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to Australia and occurs off

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

References

* Hedley, C. 1922. ''A revision of the Australian Turridae.'' Records of the Australian Museum 13(6): 213–359, pls 42–56 * {{DEFAULTSORT:Scrinium Impendens impendens Gastropods described in 1909 Gastropods of Australia