''Pyrgocythara helena'' 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

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 attains 3.5 mm, its diameter 1.25 mm. (Original description) The minute, solid shell is pale yellowish brown. It is strongly sculptured. The protoconch of about two

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 is low and rapidly increasing. The last one is keeled, otherwise smooth. . The four subsequent whorls show a deeply constricted, not appressed suture. The axial sculpture consists of (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 ...

seven) strong ribs. These are angulated at the periphery, with subequal deep interspaces, and which are not continuous up the spire. The spiral sculpture consists of on the upper whorl one, on the third two, on the body whorl about seven obscure rounded rather coarse threads with narrower interspaces. The aperture is narrow. The

anal sulcus The anal sulcus, also called the anal sinus or anal canal, in Gastropods is a notch, a shelly tube at the top of the aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and fo ...

is shallow close to the suture. The outer lip is varicose and smooth within. The inner lip is smooth. The columella is short and straight. 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 not differentiated from the aperture.Dall (1919) Descriptions of new species of Mollusca from the North Pacific Ocean; Proceedings of the U.S. National Museum, vol. 56 (1920)

Distribution

This marine species occurs in the Sea of Cortez, Western Mexico and off

Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

References

External links

* * {{DEFAULTSORT:Pyrgocythara Helena

helena Helena may refer to: People *Helena (given name), a given name (including a list of people and characters with the name) *Katri Helena (born 1945), Finnish singer *Helena, mother of Constantine I Places Greece * Helena (island) Guyana * ...

Gastropods described in 1919