''Seguenzia stephanica'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of extremely small deep water

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Seguenziidae Seguenziidae is a family (biology), family of very small deepwater sea snails, marine (ocean), marine gastropod mollusks in the superfamily Seguenzioidea (according to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastr ...

.WoRMS (2013). ''Seguenzia stephanica'' Dall, 1908. Retrieved through:

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...

at http://www.marinespecies.org/aphia.php?p=taxdetails&id=492446 on 2013-06-10

Description

(Original description of ''Seguenzia caliana'' by W.H. Dall) "The shell is small, its height attains 4.5 mm and its diameter is 3.2 mm. The white shell is elevated, trochiform, with a minute glassy smooth nucleus and about five subsequent

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). In nature File:Photograph and axial plane floral diagra ...

s. The suture is obscure, and laid on the peripheral keel. On 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. Spire ...

there is a single sharp prominent keel somewhat behind the central line between the sutures, and on the

body whorl The body whorl is part of the morphology (biology), morphology of the gastropod shell, 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 ...

is a similar peripheral keel with a wide excavated space on each side of it, the space behind the periphery wider. The base of the shell shows seven rather close-set squarish cords, those nearer the axis most adjacent to each other. The axial

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

consists of low thin sharp lamellae with wider interspaces, over riding the peripheral keel on the spire but not on the body whorl. They are prominent in the interspaces behind the base, retractively arcuate in the posterior interspace, and protractively arcuate in the others. They do not invade the somewhat flattish base. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

has a very deep sulcus next to the suture. The outer

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

in front of it is much produced, a feeble sulcus at the middle of the base. In front of the arcuate

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

there is a smaller rounded indentation. Behind the columella there is a deep groove ending in a minutely perforate

umbilicus Umbilicus may refer to: *The navel or belly button *Umbilicus (mollusc), a feature of gastropod, Nautilus and Ammonite shell anatomy *Umbilicus (plant), ''Umbilicus'' (plant), a genus of over ninety species of perennial flowering plants *Umbilicus ...

. The body has no perceptible glaze." (Original description of ''Seguenzia certoma'' by

W.H. Dall William Healey Dall (August 21, 1845 – March 27, 1927) was an American naturalist, a prominent malacologist, and one of the earliest scientific explorers of interior Alaska. He described many mollusks of the Pacific Northwest of North America, ...

) "The white, trochiform shell is small, its height attains 5 mm and it is 3.5 mm wide. It has a minute, smooth globular nucleus and seven subsequent strongly sculptured

s. The suture is obscure. The spiral

consists of a small, closely beaded thread at the summit of the whorl, separated from a low, sharp carina by a wider, excavated interspace, and the latter from a more prominent peripheral carina by a still wider space. On the base of the shell there are three sharp threads followed by three lower rounded threads, which approach the

. The axial sculpture consists of fine, even, arcuate wrinkles, which, except where they bead the posterior thread, are chiefly visible in the interspaces. The suture is laid on the peripheral thread. Between it and the outer

at the

there is a very deep sulcus. The outer lip is much produced and its edge modified by the external sculpture, so that there is a sulcus at the end of the peripheral keel, another one at the middle of the base, and still another at the base of the columella, which is arcuate and produced like a small plait. The base is imperforate. The body has no visible glaze."Dall (1919) Descriptions of new species of Mollusca from the North Pacific Ocean; Proceedings of the U.S. National Museum, vol. 56 (1920)
/ref>

Distribution

This species occurs in the Pacific Ocean from the

Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...

, Alaska (175°E) to

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

(3° S) between depths of 750 m to 5100 m; also off

La Jolla La Jolla ( , ) is a hilly, seaside neighborhood in San Diego, California, occupying of curving coastline along the Pacific Ocean. The population reported in the 2010 census was 46,781. The climate is mild, with an average daily temperature o ...

and

San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...

, California.

References

External links

Dall, W. H. (1908). Reports on the dredging operations off the west coast of Central America to the Galapagos, to the west coast of Mexico, and in the Gulf of California, in charge of Alexander Agassiz, carried on by the U.S. Fish Commission steamer "Albatross," during 1891, Lieut.-Commander Z.L. Tanner, U.S.N., commanding. XXXVII. Reports on the scientific results of the expedition to the eastern tropical Pacific, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer "Albatross", from October, 1904 to March, 1905, Lieut.-Commander L.M. Garrett, U.S.N., commanding. XIV. The Mollusca and Brachiopoda. Bulletin of the Museum of Comparative Zoology. 43(6): 205-487, pls 1-22

Dall, W. H. (1919). Descriptions of new species of Mollusca from the North Pacific Ocean in the collection of the United States National Museum. Proceedings of the United States National Museum. 56 (2295): 293-371

Geiger, D. L. (2019). The Family Seguenziidae Verrill, 1884 in the Northeast Pacific, including a comment on excessive numbers of taxonomic data portals. Zoosymposia. 13(1): 61-69

Encyclopedia of Life

USNM Invertebrate Zoology Mollusca Collection

World Register of Marine Species

Biodiversity Heritage Library (2 publications)

Encyclopedia of Life

USNM Invertebrate Zoology Mollusca Collection

ITIS

World Register of Marine Species

Biodiversity Heritage Library (1 publication)

Encyclopedia of Life

USNM Invertebrate Zoology Mollusca Collection

ITIS

World Register of Marine Species
{{Taxonbar, from1=Q14326711, from2=Q3736201, from3=Q3735679 stephanica Gastropods described in 1908