''Aforia circinata'', common name the ridged turrid, 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 ...

Cochlespiridae Cochlespiridae is a Taxonomy (biology), taxonomic family (biology), family of predatory sea snails, marine gastropod mollusks in the superfamily Conoidea. This family is not well differentiated morphologically, and there is poor congruence betwe ...

Description

The shell grows to a length of 75 mm. The slender, elongate shell is covered with a brownish epidermis. There are six evenly rounded

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 ...

, but with a sharp carina, above which they are smooth, whilst below it they are grooved, with wider interspaces. The anal sinus is deep, about one-third of the way from the carina to the suture. (Original description) The shell is slender, elongate and covered with a brownish epidermis. It contains six

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 , with a single, sharp, narrow carina, about the middle of the whorl in the upper whorls. This carina does not interrupt the even rotundity of the whorls so as to produce any flattening of the latter, but appears as if it had been placed upon the equator of the whorl, after the latter had been completed. The posterior surface of the carina and that part of the whorls behind it, are destitute of any but the most microscopic revolving striae, though plainly marked by the deeply notched lines of growth. The anterior surface of carina and whorls is covered with sharp, revolving grooves, with wider interspaces, being about twelve on 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 ...

, between the posterior edge of the aperture and the carina. The notch is deep, and about one-third of the way from the carina to the suture. 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 ...

and 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 ...

are long and narrow. The outer lip, before the carina, is effuse. The nucleus is white. W.H. Dall, Descriptions of new Species from the Coast of Alaska with notes of some rare forms; Proceedings of the California Academy of Sciences ser. 1 vol. 5 p. 61 (1873)
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Distribution

This marine species occurs in the

Bering Sea The Bering Sea (, ; rus, Бе́рингово мо́ре, r=Béringovo móre) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and The Ameri ...

and in cold waters from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

to Japan

References

* Hasegawa K. (2009) ''Upper bathyal gastropods of the Pacific coast of northern Honshu, Japan, chiefly collected by R/V Wakataka-maru''. In: T. Fujita (ed.), Deep-sea fauna and pollutants off Pacific coast of northern Japan. National Museum of Nature and Science Monographs 39: 225–383. * Hasegawa K. & Okutani T. (2011) ''A review of bathyal shell-bearing gastropods in Sagami Bay''. Memoirs of the National Sciences Museum, Tokyo 47: 97–144. 5 April 2011

External links

*
Aurivillius, C.W.S. 1885. ''Öfversigt öfver de af Vega-Expeditionen insamlade arktiska Hafmollusker. II. Placophora och Gastropoda''. In: Nordenskiöld, A.E. (Ed.) Vega-Expedionens Vetenskapliga Iakttagelser, 4: 313–383, pls. 12-13
{{DEFAULTSORT:Aforia Circinata circinata Gastropods described in 1873