''Steromphala divaricata'', common name the divaricate gibbula, is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

of small sea snail, known as top snails or top shells,

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 molluscs in the family

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.MolluscaBase eds. (2020). MolluscaBase. Steromphala divaricata (Linnaeus, 1758). Accessed through: World Register of Marine Species at: http://marinespecies.org/aphia.php?p=taxdetails&id=576618 on 2020-12-30

Distribution

It is found 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 Balkans, 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) ...

and the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, ...

Description

The length of the shell is between 12 mm and 24 mm and is 16 mm to 19 mm wide. The conoidal shell is imperforate or narrowly perforate. It is very thick and solid, cinereous. The color of the shell is yellowish or green. It is longitudinally marked with rose-red lines, often oblique or broken into square dots. 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 ...

is more or less elevated. Its outlines are rather convex. The six

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 flo ...

s are encircled by numerous lirulae, the upper ones flattened. The sutures are slightly impressed, but scalariform specimens with deep sutures are frequent. The body whorl is rounded at the periphery and on the base. 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 ...

is rounded-quadrate. The outer lip is bevelled to an edge, very thick and smooth within. The pearly

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 ...

is straightened in the middle. The

umbilicus Umbilicus may refer to: *The navel or belly button *Umbilicus (mollusc), a feature of gastropod, Nautilus and Ammonite shell anatomy * ''Umbilicus'' (plant), a genus of over ninety species of perennial flowering plants *Umbilicus urbis Romae The ...

is narrow or concealed. G.W. Tryon (1889), Manual of Conchology XI p. 207-208

References

* Costa O. G., 1829: ''Catalogo sistematico e ragionato de' testacei delle Due Sicilie''; Tipografia della Minerva, Napoli 8 + 132 p., pl. 1-3 * Brusina S., 1866: ''Contribuzione pella fauna dei molluschi dalmati''; Verhandlungen der Kaiserlich-königlichen Zoologisch-botanisch Gesellschaft in Wien 16: 1-134 * Coen G., 1937: ''Nuovo saggio di una sylloge molluscorum Adriaticorum''; Memoria Reale Comitato Talassografico Italiano 240, 1–173, 10 pls * 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 * Kantor Yu.I. & Sysoev A.V. (2006) ''Marine and brackish water Gastropoda of Russia and adjacent countries: an illustrated catalogue''. Moscow: KMK Scientific Press. 372 pp. + 140 pls.

External links

*
Linnaeus, C. (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio decima, reformata [10th revised edition
vol. 1: 824 pp. Laurentius Salvius: Holmiae]
Payraudeau B. C., 1826: ''Catalogue descriptif et méthodique des Annelides et des Mollusques de l'île de Corse''; Paris pp. 218 + 8 pl.

Costa O. G. (1830 ["1829"
Catalogo sistematico e ragionato de' testacei delle Due Sicilie. Tipografia della Minerva, Napoli. pp. 1-8, i-cxxxii, pl. 1-3">1829"">Costa O. G. (1830 ["1829"
Catalogo sistematico e ragionato de' testacei delle Due Sicilie. Tipografia della Minerva, Napoli. pp. 1-8, i-cxxxii, pl. 1-3
Monterosato T. A. (di), 1888-1889: ''Molluschi del Porto di Palermo. Specie e varietà''; Bullettino della Società Malacologica Italiana, Pisa 13 (1888[1889?
: 161-80 14 (1889): 75-81] {{Taxonbar, from=Q61684199 Steromphala, divaricata Gastropods described in 1758 Taxa named by Carl Linnaeus