''Clionella halistrepta'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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 Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Clavatulidae Clavatulidae is a taxonomic family of sea snails, marine gastropod mollusks in the superfamily Conoidea. The family is not well differentiated morphologically. Clavatulidae was raised, based on cladistic analysis, from subfamily to the family ...

Description

The size of the shell varies between 25 mm and 42 mm. (Original description) The shell has a fusiform shape. 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 are marked by a narrow, obscurely nodulous spiral keel at the summit, which is followed by a depressed spiral sulcus that equals the keel in width. The two comprise the posterior two-fifths of the whorls between the sutures. The anterior three-fifths are marked by strong, broad, low, rounded, slightly protractive axial ribs, which are strongest at their junction with the sulcus, beyond which they scarcely extend. The type has lost the early whorls; upon the first of those remaining there are 10 and upon the rest, 12 ribs. Intercostal spaces are about one-half as wide as the ribs. On account of the closely appressed summits, the sutures are poorly defined. 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 ...

is moderately long, marked by the continuations of the ribs, which gradually weaken in strength as they pass forward. The entire surface of the

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

and base are marked by lines of growth and numerous, closely crowded, fine, wavy, spiral striations. The posterior angle of the

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

is acute, sinus below the keel at the summit. The sigmoid columella is covered by a thin callus which also extends over the parietal wall, in the posterior portion of which it becomes decidedly thickened. The ground color of the shell is cream yellow. The intercostal spaces and slight extensions of their areas posteriorly across the sulcus and the summit of the keel are chestnut brown. The same coloration appears within the aperture.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)
(described as ''Clavatula halistrepta'')

Distribution

This marine species occurs off Jeffrey's Bay - East London, South Africa.

References

* Kilburn, R.N. (1985). ''Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 2. Subfamily Clavatulinae''. Ann. Natal Mus. 26(2), 417–470. * Steyn, D.G. & Lussi, M. (1998) ''Marine Shells of South Africa. An Illustrated Collector’s Guide to Beached Shell''s. Ekogilde Publishers, Hartebeespoort, South Africa, ii + 264 pp. page(s): 152

External links

* {{DEFAULTSORT:Clionella Halistrepta halistrepta Gastropods described in 1915