''Mioawateria extensaeformis'' is a 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

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

Raphitomidae Raphitomidae is a family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families". ''Malacologia'' 47(1-2). . 39 ...

Description

The length of the shell attains 8.5 mm, its diameter 4.5 mm. (Original description) The rather strong, ivory-white, ovate shell has a short spire. It contains 8 or 9

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 (the upper part is eroded) of which 3 (or 4) form a reddish-brown, convexly-whorled

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...

, of which about the two lower ones are sculptured by slightly curved riblets, crossed in their lower part by fine, oblique striae. The subsequent whorls are scarcely excavated, the place of the excavation being occupied for a great deal by a rather strong, subsutural spiral, adorned by strong, laterally compressed beads, 22 in number on 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 ...

. Below this spiral remains a rather large groove. The basal part of the whorls show narrow, a little oblique ribs, 15 in number on the body whorl, ending below the groove in short tubercles, which are connected by a second spiral. The space between the ribs is sculptured by fine and coarse growth-lines and faint spiral striae, becoming stronger and groove-like towards the base of the body whorl, and have the character of lirae on the short, large

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...

. The body whorl is regularly convex, until the siphonal canal. The aperture is oval, with a moderately sharp angle above and a wide, slightly gutter-like canal below. The peristome is broken, probably with a very shallow sinus (judging after growth-lines) . The concave columellar margin shows a thin layer of enamel. The siphonal canal is directed to the left.Schepman, 1913. The prosobranchia of the Siboga expedition. Part IV -V - VI: Toxoglossa

Distribution

This marine species was found off Western

Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...

and in the Banda Sea, at depths between 462 and 750 m

References

Sysoev, A.V. (1996b) ''Deep-sea conoidean gastropods collected by the John Murray Expedition, 1933–34''. Bulletin of the Natural History Museum of London, Zoology, 62, 1–30
* {{DEFAULTSORT:Mioawateria Extensaeformis extensaeformis Gastropods described in 1913