''Besla convexa'' 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
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* ...
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.
[Bouchet, P. (2015). Besla convexa (Carpenter, 1857). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=730707 on 2015-04-05]
Description
The small, slender shell is elongate-conic. It measures 2.4 mm. The two and one-half
whorls
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 d ...
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 ...
form a moderately elevated helicoid spire, whose axis is at right angles to that of the succeeding turns, in the first of which it is about one-fifth immersed. The six whorls of the
teleoconch overhang and are strongly contracted at the sutures, appressed at the summit, angulated at the posterior extremity of the anterior third. They are marked, between the sutures, strong, rounded, sinuous, almost vertical axial ribs, of which 16 occur upon the second and third, 18 upon the fourth, and 22 upon the penultimate turn. The intercostal spaces are a little more than twice as wide as the ribs, crossed by three equal and equally spaced cords, which are about one-half as strong as the ribs. The first of these cords is at the periphery, the third at the posterior termination of the anterior third between the sutures, which it renders strongly angulated. The sutures are constricted. The periphery and the base 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 ...
are well rounded, marked by the continuation of the axial ribs, and about eight slender spiral lirations. The
aperture is broadly oval. The posterior angle is acute. The
outer lip is thin, showing the external sculpture within. The
columella is slender, slightly curved, decidedly oblique and revolute, and is provided with a slender fold at its insertion. The parietal wall is covered with a strong callus.
William Healy Dall and Paul Bartsch , "A Monograph of West American Pyramidellid Mollusks" , Smithsonian Institution, 1909
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Distribution
The type specimen of this marine species was found in the Pacific Ocean off the coast of Mazatlán, Mexico.
References
Carpenter P.P. (1857). ''Catalogue of the collection of Mazatlan Mollusca in the British Museum collected by Frederick Reigen.'' London, xvi + 552 pp
External links
To USNM Invertebrate Zoology Mollusca Collection
World Register of Marine Species
{{Taxonbar, from=Q3140538
Pyramidellidae
Gastropods described in 1857