Tusk shell - tusk shell

Japanese: ツノガイ(角貝) - ツノガイ（英語表記）tusk shell

A general term for mollusks in the Scaphopoda class, or a single species. The shells of horn shells (scaphopoda) are tubular and usually thicken in a straight line toward the opening. They are usually curved backwards, although some species (spinning horn shells) are straight. Most are white or translucent, but they can also be greenish-blue (Elephant horn shell), yellow (Hira horn shell), or reddish purple (Elephant horn shell). The surface can be smooth or have longitudinal ribs. The opening can be circular or, depending on the ribs, 4-8-sided (Yakado horn shell), or polygonal and gear-shaped (Maru horn shell).

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

掘足綱Scaphopodaの軟体動物の総称，またはそのうちの1種を指す。ツノガイ類(掘足類)の殻は管状で殻口のほうへ通常しだいにまっすぐに太くなる。また通常背方へ弓形に曲がるが，まっすぐな種(ハリツノガイ)もある。多くは白色または半透明であるが，緑青色(ゾウゲツノガイ)や黄色(ヒラツノガイ)，赤紫色(ニシキツノガイ)のこともある。表面は平滑または縦に肋条がある。殻口は円形または肋条に応じて4～8角(ヤカドツノガイ)また多角形で歯車状(マルツノガイ)のものもある。

出典　株式会社平凡社世界大百科事典第２版について　情報

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