''Compsodrillia petersoni'' is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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 ...

Pseudomelatomidae Pseudomelatomidae is a family of predatory sea snails, marine gastropods included in the superfamily Conoidea (previously Conacea) and part of the Neogastropoda ( Bouchet & Rocroi, 2005). In 1995 Kantor elevated the subfamily Pseudomelatominae ...

Description

The length of the shell attains 28 mm, its diameter 6.7 mm. (Original description) The very elongate-conic shell is bluish white. The

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 ...

contains 2.5

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 flo ...

s, the first two well rounded, smooth, the last half crossed by a number of distantly spaced axial riblets. The postnuclear whorls are well rounded, the first with two nodulose spiral threads, the second with three, of which the median is the strongest. These remain throughout the length of the shell. In addition to this the appressed summit of the shell appears as a spiral cord. The posterior sinus is narrow and located immediately below the spiral cord at the summit. In addition to the strong spiral cords finer spiral threads are present both in the sinal sulcus near the summit and on and between the ribs anterior to this. In addition to the spiral

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 ...

the whorls are marked by axial ribs which have their beginning in the nodulose spiral threads on the first postnuclear whorl. These axial ribs are slightly protractively slanting. They extend but very slightly posteriorly to the posterior sulcus, and evanesce anteriorly on the base of the body whorl. They are more than twice the width of the spaces that separate them. Of these, 10 occur upon the first to seventh, 12 upon the eighth to tenth, and 14 upon the body whorl. These ribs and the spaces that separate them are marked by lines of growth, which also extend across the posterior sulcus and over the base and

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 ...

and give to the general surface a finely reticulated clothlike sculpture. The suture is slightly impressed. The base of the shell is well rounded, marked by four strong nodulose spiral cords like the spire and the intervening spiral threads. The

is rather long, twisted, with an obscure indication of an umbilicus at its tip, marked by seven strong, broad, rounded, very nodulose spiral cords, and six slender threads on the anterior tip. Between and on the strong cords on the columella finer threads are present. 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 ...

is rather long, strongly channeled anteriorly and posteriorly, the posterior channel almost forming a tube, since 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 ...

and the parietal callus bend forward, partly closing it. The outer lip bears a strong

varix A varix (pl. varices) is an abnormally dilated vessel with a tortuous course. Varices usually occur in the venous system, but may also occur in arterial or lymphatic vessels. Examples of varices include: * Varicose veins, large tortuous veins ...

one fifth of a turn behind its edge, and beyond this is drawn into a clawlike element, which bends in very slightly toward the aperture. The inner lip is strongly developed and projects considerably beyond the columella and extends as a rather thickened callus over the parietal wall, forming a decided knob at the termination of the posterior angle of the aperture.Bartsch, P. (1934) Reports on the collections obtained by the first Johnson-Smithsonian deep-sea expedition to the Puerto Rican deep; new mollusks of the family Turritidae. Smithsonian Miscellaneous Collections, 91, 1–29, 8 pls
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Distribution

This species occurs in the Caribbean Sea off

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

References

External links

* {{DEFAULTSORT:Compsodrillia Petersoni petersoni Gastropods described in 1934