''Bayerotrochus westralis'', commonly known as "Australia's split shell", 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

Pleurotomariidae Pleurotomariidae, common name the "slit snails", is a family of large marine gastropods in the superfamily Pleurotomarioidea of the subclass Vetigastropoda. This family is a very ancient lineage; there were numerous species in the geological pas ...

Description

The shell has a turbinate shape with an apical spire angle of approximately 90 degrees, with inflated body whorls that are proportionate in expansion so that the spire profile is straight, a clearly defined suture, and the periphery is oblique and slightly rounded. The base is highly inflated and lacks a

columellar Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the ...

callus at the center of the base area. The aperture is oval, the slit is positioned roughly one third of the way between the upper and lower sutures and is relatively long, about 19 percent of the circumference. The shell is lightly sculptured with very numerous fine spiral cords above and below the selenizone (the area where the shell growth filled in the slit), crossed by very numerous fine axial growth lines. The base has very numerous spiral striae which are crossed by numerous radial growth lines. The

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 ...

and primary whorls are white and the main body whorls are a pale buff to white color with an iridescent coppery metallic sheen. Occasionally the teleoconch (body whorls) are overlaid with pale orange or pink axial flammules. The selenizone has no distinct spiral sculpture however it has numerous fine curved growth striae. The base is the same base color as the body, and the interior of the aperture is thinly nacreous (pearly). This species is often found without a

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

. The operculum is circular, light brown, multispiral, and chitinous. Its size ranges from 44 to 130 mm in diameter.Anseeuw, P. & Goto, Y., ''The Living Pleurotomariidae'' (1996), Elle Scientific Publications, Osaka Japan, pp. 202, at pp. 154–155.

Distribution

This species has been typically found on soft muddy bottoms between 250 and 500 meters in a small area off Western Australia south of Broome and northwards to the Ashmore Reefs, off southern

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and in the Central Indo-West Pacific.

References

External links

* {{Taxonbar, from=Q4874454 Pleurotomariidae Gastropods described in 1987