''Gibbula magus'', common name the great 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 small

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 ...

mollusc 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 esti ...

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 resemb ...

, the top snails.Gofas, S. (2013). Gibbula magus (Linnaeus, 1758). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=141790 on 2014-01-28

Description

The size of the shell varies between 17 mm and 35 mm. This is an abundant species. The solid, widely, deeply umbilicate shell has a low-conical shape. There is great variation in color. It is whitish or yellowish, painted with zigzag radiating stripes, maculations or lines of pink or rich brown, sometimes so broken into minute flecks as to appear minutely mottled all over, or sometimes lacking markings. The base of the shell is radiately zigzag-striped. The apex is acute. The conical

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 ...

contains 7 to 8

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 ...

. These are swollen, gibbous and radiately plicate beneath the sutures, and with a rim or flange at the periphery. The entire surface is spirally finely striate. The base is convex. 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 very oblique, rounded-rhomboid, and smooth within. 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 ...

oblique, its edge straight or slightly convex in the middle, at its insertion reflexed slightly over the umbilicus. The umbilicus is bounded by a strong spiral rib.Tryon (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
/ref>

Distribution

This species occurs in the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

, the North Atlantic Ocean (

Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

) and 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 ea ...

References

* Coen G. (1930). Gibbula (Forskaliopsis nov. sect.) Bellinii n. sp. nuovo gasteropodo marino di Capri. Annuario del Museo Zoologico della Reale Università di Napoli (n. ser.) 6(4): 2 * Coen, G. (1937) Nuovo saggio di una sylloge molluscorum Adriaticorum. Memoria Reale Comitato Talassografico Italiano, 240, 1–173, 10 pls. * Nordsieck, F. (1982) Die Europäischen Meeres-Gehäuseschnecken (Prosobranchia). Vom Eismeer bis Kapverden, Mittelmeer und Schwarzes Meer. 2., Völlig Neubearbeitete und Erweiterte Auflage. Gustav Fischer Verlag, Stuttgart, xii + 539 pp.

External links

*
Da Costa, Mendes E. (1778). Historia naturalis testaceorum Britanniæ, or, the British conchology; containing the descriptions and other particulars of natural history of the shells of Great Britain and Ireland: illustrated with figures. In English and French. - Historia naturalis testaceorum Britanniæ, ou, la conchologie Britannique; contenant les descriptions & autres particularités d'histoire naturelle des coquilles de la Grande Bretagne & de l'Irlande: avec figures en taille douce. En anglois & françois., i-xii, 1-254, i-vii, [1
Pl. I-XVII. London. (Millan, White, Emsley & Robson)]
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]
Locard, A. (1886). Prodrome de malacologie française. Catalogue général des mollusques vivants de France. Mollusque marins. i>Lyon, H. Georg & Paris, Baillière pp. X + 778.

Griffith E. & Pidgeon E. (1833-1834). The Mollusca and Radiata. Vol. 12, In: E. Griffith, [1824
��1835, The Animal Kingdom arranged in conformity with its organization, by the Baron Cuvier, [...]. London: Whittaker and Co., viii + 601 pp., 61 pls. [Date of publication after Evenhuis (2009): pp. 1-384, Mollusca pls. 1−39, Zoophytes pls 1-20 - 1833; pp. viii + 385-601, Mollusca corrected pls. 28*, 36*, 37*, pls. 40-41 - 1834]. , available online at http://www.biodiversitylibrary.org/item/40578 page(s): pl. 1, fig. 1]
Bucquoy E., Dautzenberg P. & Dollfus G. (1882-1886). Les mollusques marins du Roussillon. Tome Ier. Gastropodes. Paris: Baillière & fils. 570 pp., 66 pls. [pp. 1-84, pls 1-10, 1882; pp. 85-196, pls 11-20, 1883; pp. 197-342, pls 21-40, 1884; pp. 343-418, pls 41-50, 1885; pp. 419-570, pls 51-66

http://www.biodiversitylibrary.org/item/55187

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
{{Commons category, Gibbula magus Gibbula, magus Gastropods described in 1758 Taxa named by Carl Linnaeus Molluscs of the Atlantic Ocean Molluscs of the Mediterranean Sea Molluscs of the Azores Invertebrates of North Africa Fauna of the North Sea