''Phorcus mutabilis'' 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 size of the shell varies between 12 mm and 24 mm. The solid, globose-conoid shell is umbilicate or subimperforate. It resembles a young ''

Phorcus articulatus ''Phorcus articulatus'' is a species of sea snail, a marine (ocean), marine gastropod mollusk in the family (biology), family Trochidae, the top snails.Gofas, S. (2012). ''Phorcus articulatus'' (Lamarck, 1822). Accessed through: World Register o ...

''. Its color is usually grayish-yellow, yellow or flesh-tinted, more or less obviously marked with obliquely radiating lines or maculations of dull crimson, sometimes broken into tessellations, sometimes faintly, minutely articulated with reddish, appearing nearly unicolored. The short

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 ...

is conoid. The suture is impressed. The 5 to 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 are slightly convex and spirally finely grooved. The body whorl is somewhat flattened around the upper part. 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 very oblique. The

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 ...

forms half of a circle. It is not so much thickened nor beveled within as in ''Phorcus articulatus''. The

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 more flattened than that of ''Phorcus articulatus''. It is scarcely edged with pearl, the tooth or lobe less heavy, more acute than that species. The umbilical region is always more excavated than ''Phorcus articulatus''. The umbilicus is open, or nearly closed by the callus at the insertion of the columella.Tryon (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
(described as ''Monodonta mutabilis'')

Distribution

This species occurs in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

, the

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to t ...

and in the Atlantic Ocean off

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

References

* Monterosato T. A. (di), 1872: ''Notizie intorno alle conchiglie mediterranee''; Palermo, Michele Amenta 61 p. * Nordsieck F., 1974: ''Il genere Osilinus Philippi, 1847 nei mari europei''; La Conchiglia 9–10 (67–68): 21–23 * Gofas S. & Jabaud A., 1997: ''The relationships of the Mediterranean trochid gastropods 'Monodonta' mutabilis (Philippi, 1846) and 'Gibbula' richardi (Payraudeau, 1826)''; Journal of Molluscan Studies 63(1): 57–64 * Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). ''European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification''. Collection Patrimoines Naturels, 50: pp. 180–213

External links

* {{DEFAULTSORT:Phorcus Mutabilis mutabilis Gastropods described in 1846 Taxa named by Rodolfo Amando Philippi