Cylichnatys angusta (A. A. Gould, 1859)

Description

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

Distribution

Western Pacific. Records include Japan. The type locality is Shimoda, Izu Peninsula, Japan.

Etymology

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

Remarks

Originally described as Haminea angusta in Proceedings of the Boston Society of Natural History 7: 139 (1859), among the shells of the United States North Pacific Exploring Expedition. Subsequently transferred to Cylichnatys T. Habe, 1952 (Cylichnidae). Junior synonyms include Cylichna kesennumaensis Nomura, 1939 (Kesennuma) and Cylichna yamakawai Yokoyama, 1928.

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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.