''Umbonium conicum'' is a

species In biology, a species is the basic unit of 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 the appropriate s ...

of very small

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

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 e ...

in the

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

Trochidae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. This family is commonly known as the top-snails because in many species the shell resembles ...

, the top snails.

Description

The height of the shell attains 5 mm, its diameter 7 mm. The polished, smooth, thin but solid shell has a conic shape with a flat base. Its color pattern is dark purple, unicolored with a reddish apex, or with an opaque white band on the lower part of each

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 floral ...

, or with the entire upper surface of the two outer whorls white, the base purple. The conical

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 ...

has straight lateral outlines. The six whorls are rather slowly widening. The

body whorl The body whorl is part of the morphology of the 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. In gastropods In gastropods, the b ...

is rounded at the periphery, flat below, or a trifle concave around the rather small, circular, dark central callus. 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 opt ...

is subquadrate and iridescent inside. The short columella is oblique, very thick and heavy, with a little nick in the edge near its base, and a slight notch where it is inserted upon the basal callus pad. The coloration is peculiar ; a beautiful iridescence glows through the purplish outer coat of the upper whorls. The conical form, flat base, and peculiarly nicked columella, together with the polished surface, smooth except for fine, impressed lines of increment, are diagnostic. ''

Umbonium thomasi ''Umbonium thomasi'' is a species of sea snail, a marine gastropod mollusk in the family Trochidae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetig ...

'' Crosse 1862, is larger and quite differently colored and sculptured.H. Pilsbry (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
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Distribution

This species occurs in the Sea of China and off

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...

References

{{Taxonbar, from=Q18356296 conicum Gastropods described in 1850