Cylichnatys angusta (A. A. Gould, 1859)

Description

A small, thin cylindrical cephalaspidean with an anteriorly amplified, obtusely rounded shell reaching about 6 mm. The shell is yellow-green, ovate-cylindrical and sculpted with transverse striations; the vertex is obliquely truncate and sub-perforate. The aperture is amplified anteriorly, and the columella is not excavated, lacking any plica or callus. It resembles Haminoea in size and form, and the soft parts retract fully into the shell.

Distribution

Type locality: Japan (material of the North Pacific Exploring Expedition). Distributed in the western Pacific, with records from the seas around Japan.

Etymology

The specific epithet angusta is the Latin feminine of angustus, "narrow" or "slender", in reference to the slender shell.

Remarks

A benthic cephalaspidean of soft sandy-mud bottoms. Junior synonyms include Cylichna kesennumaensis Nomura, 1939 (Kesennuma) and Cylichna yamakawai Yokoyama, 1928. The genus Cylichnatys (T. Habe, 1952) is now placed in the family Haminoeidae.

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References

• Haminea angusta, Gould A.A. (1859). Descriptions of new species of shells brought home by the North Pacific Exploring Expedition. Proceedings of the Boston Society of Natural History, 7: 138-142, 161-166, 169-173.
• カミスジカイコガイダマシ Cylichnatys angustus (GOULD), 波部忠重. (1961). 続原色日本貝類図鑑. 保育社, 大阪. xii + 183 + 42 pp., 66 pls. [Habe T. (1961). Coloured illustrations of the shells of Japan (II). Hoikusha, Osaka.]
• カミスジカイコガイダマシ Cylichnatys angustus (Gould, 1859), 奥谷喬司. (2000). 日本近海産貝類図鑑. 東海大学出版会.
• カミスジカイコガイダマシ, 髙重博 & 武井哲史. (2019). 日本の貝. 学研プラス.
• Oskars T.R., Too C.C., Rees D., Mikkelsen P.M., Willassen E. & Malaquias M.A.E. (2019). A molecular phylogeny of the gastropod family Haminoeidae sensu lato (Heterobranchia: Cephalaspidea): a generic revision. Invertebrate Systematics 33(3): 426-472.