''Mikadotrochus hirasei'', common name the emperor's slit shell, is a species of large deepwater

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 ...

, the slit snails.

Description

The shell has a typical trochoid shape with a spire angle of approximately 72 degrees and nearly smooth sided until the body whorls which are slightly inflated at the shoulder with a rounded periphery. The base is moderately convex to flat, and the shell has a large nacreous (pearly)

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 which covers about one third of the base and can be keeled at its outer margin. The aperture is oval, the slit is positioned mid whorl and is long, about 16 to 20 percent of the circumference. The shell is heavily textured with about 20 spiral cords crossed by numerous fine crescent shaped axial growth lines above the

selenizone A selenizone (from the Greek "selene" meaning "moon", and "zone" meaning "girdle") is an anatomical structure that exists in the shells of some families of living sea snails: the slit shells, the little slit shells and the abalones, which are m ...

(the area where the shell growth filled in the slit) and about 10 spiral cords below. The shell is creamy yellow overlaid with many crimson axial flammules above and below the selenizone which has yellowish orange crescent shaped growth marks, the base is a pale creamy yellow with occasional light crimson flammules, and the interior of the aperture is nacreous. The shell is occasionally found with part of its dark brown

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 ...

near the margin opposite the aperture. The operculum is small, dark brown, multispiral, and chitinous. Size range: 45 to 129 mm diameter.Anseeuw, P. & Goto, Y., ''The Living Pleurotomariidae'' (1996), Elle Scientific Publications, Osaka Japan, pp. 202, at pp. 98-99.Original description: Henry A. Pilsbry, in ''Proceedings of the Academy of Natural Sciences of Philadelphia, USA'' (1903) Vol. 55, "''Pleurotomaria hirisei'', n. sp."

Distribution

This species is found in deep water between 150 and 300 meters on mud and sand off the coast of the

Shima Peninsula The region of Japan, also called the , refers to the areas of eastern Mie Prefecture in or around Ise-Shima National Park, which include the cities Ise, Toba, Shima, and parts of the town of Minami-Ise. The area thrives on tourism, with many reso ...

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 ...

westwards to the Pacific coast of Shikoku Island, in the

East China Sea The East China Sea is an arm of the Western Pacific Ocean, located directly offshore from East China. It covers an area of roughly . The sea’s northern extension between mainland China and the Korean Peninsula is the Yellow Sea, separated b ...

west of

Kyushu is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surroun ...

to Taiwan, and has also been found in the central Philippines.

References

External links

* Pleurotomariidae Taxa named by Henry Augustus Pilsbry Gastropods described in 1903 {{Pleurotomariidae-stub