''Brachycythara biconica'', common name the biconic top turrid, is a species of very 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 ...
mollusk in the
family Mangeliidae.
Description
The length of the shell varies between 4 mm and 6 mm.
(Original description) The shell has a biconic shape. Its color is whitish, with a narrow spiral band of brown at the summit of the
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, which is darker between the ribs, and a similar wider band a little anterior to 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 ...
(or some specimens may be described as pale brown, with a spiral band of white on the periphery of the whorls, and as white anteriorly). The shell shows strong transverse rounded ribs, about nine on each whorl, and excessively fine spiral rather distant raised lines, which are obsolete on the summits of the ribs. 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 ...
is acute. The
spire has the outlines nearly rectilinear. It contains six whorls, subangular, with a moderately impressed suture. The
aperture is narrow. The outer
lip is often much thickened by the last rib. The sinus is near the upper extremity of the outer lip, rather large in old shells. The
siphonal canal
The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...
is short.
Distribution
''B. biconica'' can be found in Atlantic waters, ranging from the coast of
North Carolina south to
Brazil.;
[Tunnell, John W., Jr., Felder, Darryl L., & Earle, Sylvia A., eds. ''Gulf of Mexico Origin, Waters, and Biota, Volume 1: Biodiversity.'' Texas A&M University Press, 2009. 666.] in the
Caribbean Sea, the
Gulf of Mexico and the
Lesser Antilles.
References
* Clench & Turner, 1950. The Western Atlantic marine mollusks described by C. B. Adams.
* Rolán E. & Espinosa J. (1999). ''El complejo Brachycythara biconica (C. B. Adams, 1850) (Mollusca: Gastropoda: Turridae) en Cuba, con la descripción de una nueva especie''. Bollettino Malacologico, 34(1-4): 43-49
Rosenberg, G., F. Moretzsohn, and E. F. García. 2009. ''Gastropoda (Mollusca) of the Gulf of Mexico'', pp. 579–699 in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M Press, College Station, Texas
External links
Tucker, J.K. 2004 ''Catalog of recent and fossil turrids (Mollusca: Gastropoda)''. Zootaxa 682:1-1295.*
MNHN, Paris: ''Brachycythara biconica''
{{DEFAULTSORT:Brachycythara Biconica
biconica