''Fluxinella trochiformis'', common name the sundial top shell, 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), ...

of extremely small deep water

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 ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

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 ...

Seguenziidae Seguenziidae is a family (biology), family of very small deepwater sea snails, marine (ocean), marine gastropod mollusks in the superfamily Seguenzioidea (according to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastr ...

.WoRMS (2013). ''Fluxinella trochiformis'' (Schepman, 1909). Retrieved 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 catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...

at http://www.marinespecies.org/aphia.php?p=taxdetails&id=492431 on 2013-06-10

Description

(Original description by M. Schepman) The height of the shell attains 2½ mm. The white, thin shell has a conic shape. It is sharply keeled. 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 ...

contains 6

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. The nucleus is slightly umbilicate. The postnuclear whorls are nearly smooth. They show very fine curved growth striae. The whorls are nearly straight, but slightly convex in the upper part, slightly concave near the lower suture. The whorls are prominently keeled above the suture, the keel being finely crenulate. The base of the shell is a little convex, excavated towards the peripheral keel, with three fine spirals at some distance from the periphery and a few, scarcely visible ones towards the central part, moreover with numerous very fine curved growth striae. The

umbilicus Umbilicus may refer to: *The navel or belly button *Umbilicus (mollusc), a feature of gastropod, Nautilus and Ammonite shell anatomy *Umbilicus (plant), ''Umbilicus'' (plant), a genus of over ninety species of perennial flowering plants *Umbilicus ...

is moderately large, pervious, scalar, with a rib at its margin and a groove just around this rib. 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 subtriangular, its margins broken, the upper one convex, the basal one nearly straight. The short columellar margin is excavated, and angular below by the end of the umbilical rib. (described as ''Fluxina trochiformis'')Schepman 1908-1913, The Prosobranchia of the Siboga Expedition; Leyden,E. J. Brill,1908-13
/ref>

Distribution

This marine species occurs off

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

References

External links

Encyclopedia of Life

World Register of Marine Species
* {{Taxonbar, from=Q13636725 trochiformis Gastropods described in 1909