Retusa concentrica (A. Adams, 1850)

Description

A minute cephalaspidean reaching just a few millimetres in shell length. Shell small, sub-cylindrical and elongate, slightly dilated at the base, white, longitudinally faintly sulcate and engraved with very distinct transverse striae; the apex bears an immersed conspicuous spire surrounded by a radiately striated peromphalus. Aperture narrow and linear, anteriorly produced and posteriorly dilated; columella simple. Soft parts retract entirely into the shell. Lives on sandy mud, where it likely preys on microscopic infauna.

Distribution

Northwest Pacific, including the seas around China and Japan. The type locality is Cagayan, Philippines (Cuming collection).

Etymology

The specific epithet concentrica is the Latin for "concentric" (from con-, "together", and centrum, "centre"), in reference to the concentric transverse striations engraved on the shell.

Remarks

Originally described as Bulla concentrica by A. Adams as species 114 of his "Monograph of the Family Bullidae" in Thesaurus Conchyliorum, vol. II (Sowerby, London, 1850–1854; pl. 125 fig. 146). Subsequently transferred to Retusa Brown, 1827 (Retusidae).

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References

• Bulla concentrica, Adams A. (1850-1854). Monograph of the Family Bullidae. In: Sowerby G.B. II (ed.) Thesaurus Conchyliorum, or Monographs of Genera of Shells. Vol. II (Part XVI-XVII): 553-608, pls. 119-125. Sowerby, London.
• コウシボリコメツブガイ Retusa (Coleophysis) concentrica (A. Adams, 1855), 奥谷喬司. (2000). 日本近海産貝類図鑑. 東海大学出版会.