''Ilanga laevissima'' 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 ...

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 ...

Solariellidae Solariellidae is a family of small sea snails, marine gastropod mollusks in the superfamily Trochoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).Gofas, S. (2011). Solariellidae. Accessed through: World Register of ...

.WoRMS (2012). ''Ilanga laevissima'' (Martens, 1881). Accessed through:

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialist ...

at http://www.marinespecies.org/aphia.php?p=taxdetails&id=567651 on 2012-12-03

Description

The size of the shell varies between 9 mm and 22 mm. The shell is broadly umbilicated and 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 ...

has a depressed conoidal shape. It is sculptured with very fine, hardly visible spiral striae and is otherwise smooth. It is very shining, ashen-whitish, painted with light yellowish to light brown confluent flammules above and at the umbilicus. It is ornamented with waved zigzag and acutely angular light and dark brown streaks. The 5½

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 ...

s are slightly convex, moderately sloping, separated by simple, deep-channeled sutures. The spire shows only here and there very faint traces of obsolete spiral striae. The broad

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 ...

convex above with small erect slightly angular nodules in three rows, the two rounded at the periphery, depressly convex at the base. The rather large and deep umbilicus is cylindrical. It is bordered on the outer edge by an obtuse angle, a second angle appearing a little way within the orifice. The space between the two angles is slightly flattened, numerous very distinct close-set plicae traverse this space, crossing the angles. The rather large, diagonal

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 rounded-trapezoidal. The thin, simple

peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes. In mosses In mosses, ...

is incomplete. The columellar margin is straightened, forming an obtuse angle where it joins the basal

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 ...

. The outer lip is sloping above, rounded at the base. The horny, concave operculum is thin with 6-7 whorls and has a raised lamina at the suture of the whorls.G.B. Sowerby III (1904) Mollusca of South Africa; Marine investigations in South Africa , v. 2 (1904)
(described as ''Minolia congener'')

Distribution

This marine species occurs off Zululand to the Atlantic

Cape Province The Province of the Cape of Good Hope ( af, Provinsie Kaap die Goeie Hoop), commonly referred to as the Cape Province ( af, Kaapprovinsie) and colloquially as The Cape ( af, Die Kaap), was a province in the Union of South Africa and subsequen ...

, South Africa

References

* von Martens 1881: Anschluss an frühere Mittheilungen mehrere neue Arten von Conchylien vor, theils aus Central-Asien (vergl. October 1879), theils von den Sammlungen Sr. M. Schiff Gazelle (vergl. Februar und Juli 1878) herrührend. 65; Sitzungs-Bericht der Gesellschaft naturforschender Freunde zu Berlin v.4 p. 63-67

External links

To World Register of Marine Species
* {{Taxonbar, from=Q5997111 laevissima Gastropods described in 1881