''Theta spicea'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

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" ...

.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 i ...

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). In nature File:Photograph and axial plane floral diagra ...

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 The body whorl is part of the morphology (biology), morphology of the gastropod shell, 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 ...

. 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. Spire ...

. 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 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 ...

. 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-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

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: ) 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 ...

, 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, 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 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, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

References

External links

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