''Turbonilla approximata'' 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 Pyramidellidae, the pyrams and their allies.Rosenberg, G. (2011). ''Turbonilla approximata'' Dall & Bartsch, 1906. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=588583 on 2012-03-01

Description

The white shell has a tapering, elongate-conic shape. Its length measures 8.2 mm. The whorls of the

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...

are decollated. The 13

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 of the teleoconch are flattened, slightly shouldered, and ornamented by strong, rather narrow, oblique, axial ribs. These are distinct at the summit but fuse at the periphery. Twelve of these ribs appear on the first, fifteen upon the fifth, eighteen upon the tenth, and twenty-two upon the penultimate whorl. The intercostal spaces are a little wider than the ribs, decidedly depressed, and terminating suddenly at the periphery. The summit of the succeeding whorls falls a little anterior to the termination of the intercostal spaces and leaves a very narrow smooth area above the well-marked sutures. 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 slightly angulated. The base of the shell is moderately long and well rounded. The subquadrate aperture is moderately large. The posterior angle is acute. The outer lip is thin, showing the external sculpture within by transmitted light. The columella is slender, oblique, and somewhat revolute. The columellar fold is not apparent in the aperture. The parietal wall is covered by a thin film of callus.Dall & Bartsch (1906), Notes on Japanese, Indopacific and American Pyramidellidæ; Proceedings of the National Museum, vol. XXX # 1452; p. 337-338
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Distribution

This species occurs in the pacific Ocean off

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and the Solomon Islands.

References

External links

To World Register of Marine Species
{{Taxonbar, from=Q7853952 approximata Gastropods described in 1906