''Addisonia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of sea snails, marine gastropod

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 es ...

s in the

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

Addisoniidae Addisoniidae is a family of sea snails, deepwater true limpets, marine gastropod mollusks in the clade Vetigastropoda Vetigastropoda is a major taxonomic group of sea snails, marine gastropod mollusks that form a very ancient lineage. ...

Description

The ovate shell has a subconical shape. It is strongly symmetrical, porcellaneous, and thin. The blunt

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

is curved backward, downward, and to the left. The shell has no

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...

. The margin is unthickened, simple, and entire. The pedal muscular impression is horseshoe-shaped and interrupted in front. The

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

has a large simple rhachidian tooth with, on each side, two large, simple transverse laterals, followed by two minute ones, and a large outer lateral with a strong tridentate cusp, outside of which is a single scale-like flat uncinus, bearing an elongated thickened ridge, but no cusp. Soft parts : the head is provided with two tentacles without eyes or eye tubercles. The muzzle is plain and simple. The foot is thin, orbicular, without lateral or posterior tubercles, processes or fringes. The mantle edge is simple and thickened. The gill is composed of leaflets as in ''

Patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

'', the series starting on the right behind the head and continued within the mantle edge backward. The body of the animal is asymmetrically placed with regard to 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 ...

of the shell to afford room for the enormous series of branchial leaflets. The anus opening is behind and above the head slightly to the right of the median line, and indicated by a small papilla.

Species

Species within the genus ''Addisonia'' include: * '' Addisonia brophyi'' McLean, 1985 * '' Addisonia excentrica'' (Tiberi, 1855) ; Species brought into synonymy : * ''Addisonia enodis'' Simone, 1996 : synonym of ''Addisonia excentrica'' (Tiberi, 1855) * ''Addisonia lateralis'' (Requien, 1848): synonym of ''Addisonia excentrica'' (Tiberi, 1855) * ''Addisonia paradoxa'' Dall, 1882: synonym of ''Addisonia excentrica''

References

* Mc Lean J. H. (1985). ''The Archaeogastropod Family Addisoniidae Dall, 1882: life habit and review of species''. The Veliger 28 (1): 99-108 etails* Roldan E. & Luque A. (2010) ''The ecology, biology and taxonomy of Addisonia excentrica (Tiberi, 1855) (Cocculiniformia: Addisoniidae) from southern Spain''. Journal of Molluscan Studies 76:201-210.

External links

{{Taxonbar, from=Q3168879 Addisoniidae