''Mitromorpha axicostata'' 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 ...

Description

The length of the shell attains 4.9 mm, its diameter 2.1 mm. (Original description) The solid shell has an elongate-oval shape. It consists of 6

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 pointed

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 2½ smooth convex whorls. The whorls of the

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. Spires are ...

are slightly convex. The suture is simple and is margined by a flat, narrow band. The base of the shell is moderately 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 elongate-oval, slightly constricted into a short, open

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 ...

. The outer lip is thin, simple, convex in profile, with a shallow, wide depression just belowi the ascending suture. The inner lip is complete and has an applied thin glaze, callous at the suture. The columella is long, nearly straight, slightly prominent at the junction with a concave base of 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 ...

. No definite plait. The sculpture sconsists of oblique rounded axial ribs, as wide as the interspaces, absent from the base, and vanishing towards the aperture. The spiral lirae are flatly convex, wider than their spaces, cross the ribs, nine in the penultimate, twenty-five in the body whorl. When fresh there is a walnut-coloured band over the middle third of the body whorl, less extensive in the intercostal spaces. This appears above the suture in the spire whorls; the ribs are dotted above, and there are curved axial lines of dots on the lirae at the base. The size may reach to—Length, 73 mm. ; of the body-whorl, 36 mm. :breadth, 3 mm. The ribs in the longer form may be much narrower, and may be obsolete before reaching the body whorl.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 33: 293–342

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

External links

* {{DEFAULTSORT:Mitromorpha Axicostata axicostata Gastropods described in 1909 Gastropods of Australia