''Gymnobela agassizii'' is a species of

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 ...

Raphitomidae Raphitomidae is a Family (biology), family of small to medium-sized sea snails, marine (ocean), marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families" ...

. Subspecies: ''Gymnobela agassizii mexicana'' (Dall, 1889) (synonym: ''Pleurotomella agassizii mexicana'' Dall, 1889)

Description

The length of the shell attains 47 mm, its diameter 14 mm. The shell is large and handsomely

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 ...

d. It contains eight convex

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, shouldered, with about sixteen thick, rounded, oblique ribs, separated by concave interspaces. The ribs do not extend above the shoulder, leaving a rather broad flattened band, which is covered by raised revolving lines, more or less decussated by prominent growth lines and slight riblets, running down the suture. The revolving lines become stronger and more elevated below the shoulder, and cross the ribs as well as their intervals. Towards 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 i ...

the ribs fade out and the revolving lines become still more prominent. 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 ...

has a wide and rather deep rounded notch below the suture. Below this, it curves strongly forward and recedes again at the siphonal canal, which is rather short, narrowed and a little excurved. The

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 ...

is smooth, curved, and obliquely narrowed at the siphonal canal. 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 ...

is subovate, sinuous and rather large. The shell is white, except the columella which is stained with orange-brown.

Distribution

''G. agassizii'' can be found in Atlantic waters, ranging from the coast of

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

south to

Tobago Tobago, officially the Ward of Tobago, is an List of islands of Trinidad and Tobago, island and Regions and municipalities of Trinidad and Tobago, ward within the Republic of Trinidad and Tobago. It is located northeast of the larger islan ...

.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. 668.

References

External links

Verrill A. E. (1885). ''Third catalogue of mollusca recently added to the fauna of the New England Coast and the adjacent parts of the Atlantic, consisting mostly of deep sea species, with notes on others previously recorded.'' Transactions of the Connecticut Academy of Arts and Sciences, 6: 395-452, pl. 42-44
*
Bouchet & Warren, Revision of the North-East Atlantic bathyal and abyssal Turridae (Mollusca, Gastropoda); The Journal of Molluscan Studies, supplement 8, December 1980
{{DEFAULTSORT:Gymnobela Agassizii agassizii Gastropods described in 1880