''Gibbula tryoni'' is a species of

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 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 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 ...

mollusk in the family Trochidae, the top snails.Rosenberg, G. (2012). ''Gibbula tryoni'' Pilsbry, 1889. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=599741 on 2012-11-23

Description

The size of the shell attains 17 mm. The umbilicate, rather thin shell has a conical shape. It is crimson or purplish red, obscurely, rather finely mottled with arrow-shaped whitish dots, usually with several narrow articulated lines on the base, and in the middle of the upper surface of the

body whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

. The yellow, apical

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 eroded. The spire is conic. The five whorls are a little tumid below each suture, and with a narrow ledge or margin, marked off by an impressed line, above each suture. This peripheral ledge gives the body whorl a rather prominent keel. The surface is polished, but shows quite prominent, spaced, impressed growth lines, and under a lens is all over very densely minutely spirally striate. The base of the shell is flattened, rather prominent around the umbilicus. The oblique aperture is quadrangular, smooth and with a very brilliantly iridescent green nacre inside. The columella is arcuate above and expanded partly over the umbilicus. The parietal wall is free from callus. The umbilicus is deep, with a narrow rapidly tapering perforation, but broad and funnel-shaped at the opening. (Description of Gibbula medusa by Bartsch) The height of the shell attains 3.5 mm, its diameter 5 mm. The shell has a depressed conic shape. The nuclear

s are white. The postnuclear whorls are marked with broad axial bands of brown which may extend entirely across the whorls, or may be interrupted in the middle. These bands of brown are separated by spaces of a light sage green, which are about as wide as the brown bands on the posterior half of the whorls between the sutures. The green area fading to yellow anteriorly. These light areas are speckled with small dots of chestnut and clouded in places with pale brown. The base of the shell is pale green, profusely spotted with dots and blotches of red. The 2¼ nuclear whorls are depressed helicoid. The postnuclear whorls are evenly rounded, marked with two, broad, spiral bands, which extend over the anterior half of the whorls between the sutures, where they appear as two turns of a bandage. The periphery of the

is marked by a moderately strong spiral keel which renders it angulated. The sutures are feebly constricted. The base of the shell is short, well rounded, and broadly umbilicated. It is marked by seven broad low bands which grow successively wider from the umbilical edge toward the periphery. These bands appear as a series of turns of a bandage. The umbilicus lacks any spiral sculpture. The entire surface of spire and base is marked with faint retractive lines of growth. The oval aperture is very oblique. The outer and basal lips are thin, showing the external markings within. The inner lip is quite thick, evenly curved. The parietal wall is glazed with a very thin callus. In 1963 K.H. Barnard considered this name a synonym and a juvenile form of ''Gibbula tryoni'' Pilsbry, 1889 Contributions to the knowledge of South African marine Mollusca; Annals of The South African Museum vol. 47; 1963
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Distribution

This marine shell occurs off

Port Elizabeth Gqeberha (), formerly Port Elizabeth and colloquially often referred to as P.E., is a major seaport and the most populous city in the Eastern Cape province of South Africa. It is the seat of the Nelson Mandela Bay Metropolitan Municipality, Sou ...

and

Port Alfred A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Ha ...

to North KwaZuluNatal, South Africa

References

External links

To Biodiversity Heritage Library (3 publications)

To World Register of Marine Species

P. Bartsch (1915), Report on the Turton collection of South African marine mollusks, with additional notes on other South African shells contained in the United States National Museum; Bulletin of the United States National Museum v. 91 (1915)
{{Taxonbar, from=Q5559048 tryoni Molluscs of the Indian Ocean Gastropods described in 1889 Taxa named by Henry Augustus Pilsbry