''Gibbula rifaca'' 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

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.

Description

The height of the shell attains 3.5 mm, its diameter 5 mm. The sublenticular shell is, wax colored, with irregular blotchings and spottings of very pale chestnut brown. The upper surface is depressed and has a helicoid shape. The nucleus consists of a little more than one

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 ...

, which is well rounded and smooth. The 3½ postnuclear whorls are marked by strongly incised spiral lines, causing the space between them to appear as raised, well rounded spiral cords on the first two postnuclear whorls and as broad flattened cords on the last whorl. Eight of these spiral cords appear on the first, seven on the second, while on the last turn 12, including the peripheral cord, appear between the periphery and the summit. Those nearest the periphery on this whorl are much narrower than on the posterior portion of the whorl. The sutures are well marked. The periphery 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 ...

is very strongly angulated. The base of the shell is very short, slightly concave, broadly, openly umbilicated, and marked by 12 depressed, rounded spiral cords of somewhat varying width. The entire surface of the shell is marked by slender lines of growth which extend over the base and into the umbilicus. The large aperture is very oblique. The thin outer lip shows the external sculpture within. The inner lip is almost vertical, sinuous, reflected over and appressed to the preceding whorl.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)
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Distribution

This marine species occurs off

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 ...

, South Africa.

References

{{DEFAULTSORT:Gibbula Rifaca rifaca Gastropods described in 1915