''Abyssochrysos melvilli'', common name Melvill's abyssal shell, 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

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 ...

mollusc 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 esti ...

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 ...

Abyssochrysidae.

Description

(Original description by M. Schepman) The size of the shell varies between 10 mm and 50 mm. The small, white shell has a pyramidal shape. 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 ...

consists of 11½

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 of which nearly 2 form the nucleus. The first whorl is rather bulbous and smooth. The second whorls is radiately ribbed and also swollen. The remaining whorls increase regularly in size. They are slightly contracted above and below, nearly straight towards the middle, with two spiral rows of pointed nodules, connected by slight spirals and oblique radiating ribs. Moreover, the shell has a thin spiral, just above the linear suture. The rest of the surface is smooth and shining, with a slight nacreous lustre and with numerous fine growth striae. 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 conspicuously keeled below the periphery and with a second keel at some distance on the smooth base. 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 subrhombic. The outer margin is thin, angulate at the end of the lower row of nodules. The columellar margin is rounded, slightly curved, ending in a point, where it joins the basal margin. M.Schepman was much puzzled by this species and couldn't readily place it. He tentatively placed it in the genus ''Argyropeza''.Schepman 1908-1913, The Prosobranchia of the Siboga Expedition; Leyden,E. J. Brill,1908-13
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Distribution

This species occurs in the Southwest Pacific Ocean and off Southeast Africa.

References

* Bouchet P. (1991). ''New records and new species of Abyssochrysos (Mollusca, Caenogastropoda).'' Journal of Natural History 25(2): 305–313

External links

* {{DEFAULTSORT:Abyssochrysos Melvilli melvilli Gastropods described in 1909