''Charisma arenacea'', common name the sandy charisma, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of extremely 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 ...

, a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

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 ...

Trochidae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. This family is commonly known as the top-snails because in many species the shell resembles ...

, the top snails.Marshall, B. (2013). Charisma arenacea (Pritchard & Gatliff, 1902). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=720369 on 2014-03-11

Description

The height of the shell attains 2 mm, its diameter also 2 mm. The small, solid, umbilicate shell has a turbinate shape. Its color is sordid white. The four to five

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 are convex. The nuclear whorls are smooth, the rest are spirally ridged. These ridges are well-developed and number about 11 to 13 around the circular

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 ...

on 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 space between the ridges is wider than the ridges. The umbilicus is deep and extends at the back of the columella to the anterior of the aperture. It is occasionally margined by a strong thread. The base of the shell is round. The lip is thick.Pritchard, G.B. & Gatliff, J.H. 1902. ''On some new species of Victorian mollusca,'' No. 5. Proceedings of the Royal Society of Victoria n.s. 14(2): 180-184, pls 9-10
/ref>

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 ...

, Victoria and

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

References

* Cotton, B.C. 1959. ''South Australian Mollusca. Archaeogastropoda''. Handbook of the Flora and Fauna of South Australia. Adelaide : South Australian Government Printer 449 pp

External links

To World Register of Marine Species

Gastropods.com: ''Charisma arenacea''
{{Taxonbar, from=Q16975630 arenacea Gastropods of Australia Gastropods described in 1902