Wedge shell - Wedge shell

Japanese: ナミノコガイ(浪子貝) - ナミノコガイ（英語表記）wedge shell

A bivalve of the family Mytilidae (illustration). The shell is 1.6 cm high, 2.4 cm long, and 0.9 cm wide, and is flattened and rounded triangular. It is thick and solid, with the apex of the shell being wider at the rear and narrowing toward the front. The shell surface is smooth at the front, but has thin radial ribs at the rear. There is considerable variation in color among individuals, ranging from white to blackish brown, with many individuals having radial color bands. It is widely distributed from the Boso Peninsula south to the tropical Pacific and Indian Oceans, and lives on sandy beaches in the intertidal zone. At high tide, it pops out of the sand from the low tide zone with each rising tide and rides the waves to the high tide zone, and at low tide, it does the opposite, popping out of the sand with each falling tide and riding the waves back to the low tide zone.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

フジノハナガイ科の二枚貝（イラスト）。殻の高さ1.6cm，長さ2.4cm，幅0.9cmに達し，扁平で丸みのある三角形。厚く堅固で，殻頂は後方によって後端は広く前方へ狭くなる。殻の表面は前方では平滑であるが，後方では細い放射肋が出る。色彩は個体変異が著しく，白色から黒褐色まであり，放射状の色帯を有する個体が多い。房総半島以南～熱帯太平洋，インド洋に広く分布し，潮間帯の砂浜にすむ。満潮になると低潮帯から上げ潮ごとに砂中から飛び出して波にのって高潮帯へ移動し，干潮時にはそれとは逆に引潮ごとに砂中から飛び出して波にのって低潮帯へ戻る。

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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