''Retidrillia willetti'' is a species of sea snail, a marine gastropod

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 es ...

in the

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

Borsoniidae Borsoniidae is a monophyletic family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet, P. (2011). Borsoniidae. Accessed through: World Register of Marine Species at http://www.marinespecies.or ...

.BWoRMS (2015). Retidrillia willetti. In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=434869 on 2016-03-23

Description

The length of the shell attains 10 mm, its width 4.5 mm. (Original description) The small, white shell has a pale operculum with an apical

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also calle ...

. The whorls of the protoconch are translucent white, glassy, inflated, about one and a half in number, then gradually passing into the reticulate

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 ...

of the five or six subsequent turns. The suture is appressed with one or two close-set prominent spiral threads in front of it. The whorls are sloping forward flatly from these threads to an angle at the shoulder forming the periphery. This part of the whorl is minutely spirally threaded. The other spiral sculpture consists of (on the base about five) strong threads with wider interspaces containing minor threads all merging toward and on 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 ...

into a series of subequal close-set threads. The anal fasciole has its deepest part at the shoulder angle, but the arcuate incremental lines on the whorl behind the angle indicate that it was when complete wide and shallow. The axial sculpture consists of (on the penultimate whorl about 16) strongly protractive short ribs starting at the shoulder, which they slightly nodulate, and reaching to the suture, but obsolete on the body whorl and not reaching much beyond the periphery The outer

lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

is thin and sharp. The inner lip is erased. The

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the ...

is short and obliquely attenuated in front. The siphonal canal is short, distinct and slightly recurved.Dall (1919) Descriptions of new species of Mollusca from the North Pacific Ocean; Proceedings of the U.S. National Museum, vol. 56 (1920)
(described as ''Suavodrillia willetti'')

Distribution

This marine species occurs off Southeastern

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 ...

References

External links

Bouchet P., Kantor Yu.I., Sysoev A. & Puillandre N. (2011) A new operational classification of the Conoidea. Journal of Molluscan Studies 77: 273–308.
{{DEFAULTSORT:Retidrillia Willetti willetti Gastropods described in 1919