''Theta spicea'' 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 ...

Raphitomidae Raphitomidae is a family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families". '' Malacologia'' 47(1-2). . 3 ...

.MolluscaBase eds. (2020). MolluscaBase. Theta spicea (R. B. Watson, 1881). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=533494 on 2020-04-09

Description

The length of the shell attains 6.4 mm. (Original description) The shell is short and broad, biconical, scalar, angulated, without ribs, but with tubercles at the angle, and feeble spiral threads on the base. 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 small and lop-sided.

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 ...

: ''Longitudinals''— there are none but very fine, unequal, hairlike lines of growth. ''Spirals'' —immediately below the suture is a minute collar of very small, high, round, remote tubercles, whose sutural surface at right angles to the axis is perfectly flat. This collar is strongest on the earlier

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. Below this is a sloping, flat, or slightly concave shoulder. A little above the middle of the whorls is a rectangular angulation beset with small, remote, slightly elongated, sharpish tubercles, which give the appearance of a sharply expressed keel. Of these tubercles there are about twenty-seven on the body whorl. But they diminish rapidly up 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. Spires are ...

. The base of the body whorl is defined by a small rounded thread, which forms a feeble keel. It lies quite below the origin of 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 ...

. A little remotely below it lie two or three others, rather weaker, but prominent, widely parted, rounded threads, with four or five similar ones on the siphonal canal, of which the last one or two are stronger than the others. The colour of the shell is polished porcellaneous white. The spire is scalar and stumpily conical, with its profile-lines much interrupted by the constriction of the sutures. The

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

consists of two embryonic whorls. It is large and dome-shaped, having the extreme tip quite immersed and the suture almost suppressed. The shell contains 5½ whorls in all (but the specimen is immature). They are short and broad, of rather rapid increase, with a broad horizontal shoulder and a sharp carinated angle, below which they are cylindrical with a slight contraction to the lower suture. The last is broadest at the keel, a little contracted below this point, tumid on the base, drawn in at 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 ...

, with a small, short sharp-pointed, siphonal canal. The suture is very strong and distinct, from the concave curve of the whorl above it and the horizontal tabulation of the collar below. 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 largish, angularly pear-shaped. The outer

thin, angulated, straight and horizontal above, convex and patulous below the angle, drawn in at the siphonal canal. It retreats at once on leaving the body to form the rather deep, narrow, rounded sinus which occupies the shoulder. Below this it descends very little, but runs out into a very convex curved edge, whose prominence is greatly increased by the rapidity and extent of the retreat of the lip-edge at the siphonal canal. The inner lip is narrowly excavated in the substance of the shell on the body and down the columella. It has a convex contour across the body, at the junction of which and the columella is a strong but rounded angle. The columella is short, strong, conical, obliquely truncated in front, with a sharp, rounded, twisted edge.

Distribution

This marine species occurs in the Atlantic Ocean off Northeast

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

References

External links

*
Gastropods.com: ''Gymnobela (Theta) spicea''
{{Taxonbar, from=Q14487108 spicea Gastropods described in 1881