Juvenile shells of three Arcidae collected in shallow waters of Kujukuri Beach were investigated. On all specimens the length, height, breadth and dorsal margin length were measured and the number of radial ribs were counted. Scapharca satowi DUNKER is roughly trigonal. Radial ribs vary in number from 29 to 38. Scapharca inaequivalvis (BRUGUIERE) is rather swollen. Radial ribs are 29 to 33 in number and those of left valve are usually verrucose on top. Scapharca broughtoni (SCHRENCK) is oval in outline. Radial ribs are 36 to 40 in number.

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