''Dillwynella houzeaui'' is an extinct species of

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 in the family

Skeneidae The Skeneidae are a speciose family of minute to small marine gastropod molluscs in the superfamily Trochoidea.Bouchet, P.; Gofas, S. (2013). Skeneidae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php ...

. Cossmann (1913), Révision des scaphopodes, gastropodes et céphalopodes du montien de Belgique; Mémoires du Musée Royal d'Histroire Naturelle de Belgique 1913
p. 36

Description

The height of the shell attains 2.5 mm, its diameter 4 mm. The rather small, nacreous shell is wider than high. The surface appears perfectly smooth and glazed with traces of brown wavy lines. The depressed spire has a conoidal shape. It consists of four barely convex

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, increasing rapidly in size under an apical angle of 160 ° on average. They are separated by linear, clearly visible sutures. 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 ...

forms almost the entire shell. It is round at the periphery which is not angular, even if both faces of the shell are rather depressed. The base of the shell is moderately convex, topped in the center with a more whitish coating that thickens toward the aperture to form a flattened and callous auricle at the end of the columellar edge and above a relatively narrow umbilical opening. The aperture is round. The peristome is discontinuous. The outer lip is oblique. The excavated columella is smooth.

Distribution

This marine species was found as a fossil in a coal mine near

Mons Mons (; German and nl, Bergen, ; Walloon and pcd, Mont) is a city and municipality of Wallonia, and the capital of the province of Hainaut, Belgium. Mons was made into a fortified city by Count Baldwin IV of Hainaut in the 12th century. T ...

in Belgium.

References

External links

{{Taxonbar, from=Q16991813 houzeaui