''Trochus radiatus'', common name the radiate top shell, 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 sea snail, a 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 e ...

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 ...

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 resemb ...

, the top snails.

Description

The thick, rather solid, trochoidal shell has a moderately elevated

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 a ...

and is false-umbilicate. Its length varies between 17 mm and 40 mm. The color of the shell is yellowish whitish, tinged with green, and radiately striped with broad or narrow uninterrupted, axial, crimson flames. The base of the shell is white or pink, radiately marked or minutely speckled with red. The aperture, columella and umbilical area are pearl white. The

has nearly straight outlines. The

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 acute, generally eroded and orange-colored. The about 7 whorls are planulate, sometimes a little concave in the middle. The body whorl has a sharply angled periphery. The shell upper surface is circled by irregularly beaded bands, 5 or 6 on each whorl, uneven in size, the upper row largest;. The bead in each whorl is larger on the upper row than those at lower rows, The base of the shell is nearly flat, concentrically lirate. These lirae are granulose, rather coarse, with broad interspaces, which are frequently occupied by revolving lirulae or striae. The oblique

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

is strongly plicate above, its edge nearly smooth and shows blunt teeth. The large

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 ...

is subrhomboidal, lirate within, and grooved. The basal

lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

thickened and crenate The umbilicus is wide and deep. The umbilical tract is funnel-shaped, rather broad, with a central rib. The parietal wall is scarcely callous, showing the color of the base, and with a white spiral rib in the middle.H. Pilsbry, Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
/ref> Normally adult and large shells are encrusted with algae. Shells washed on beaches are usually clean, exposing the underlying pearly layer below the surface. This species feeds on encrusting algae. The conspicuously radiate color pattern and the

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable ...

, consisting of coarse granulose lirae with interstitial lirulae both above and below, as well as the wide umbilical tract and eroded corneous or orange

, will serve to distinguish this form.

Distribution

This species occurs on intertidal rock boulders in the Indian Ocean off

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

and in the Western Pacific.

References

* Drivas, J.; Jay, M. (1987). ''Coquillages de La Réunion et de l'Île Maurice''. Collection Les Beautés de la Nature. Delachaux et Niestlé: Neuchâtel. . 159 pp

External links

* {{DEFAULTSORT:Trochus radiatus radiatus Gastropods described in 1791