New distributional records of two rare grapsoid crabs (Decapoda: Brachyura) from the Okinawa Island Group, central Ryukyus, Japan.

沖縄諸島の古宇利島からヨコスジイワガニPachygrapsus fakaravensis Rathbun, 1907, 沖縄島からナガレガニPlanes marinus Rathbun, 1914の標本が得られた. ヨコスジイワガニは古宇利島からの初記録であり, ナガレガニは琉球列島沿岸から初記録である. 本稿ではこれら各種と同属であるコイワガニPa. plicatus (H. MilneEdwards, 1837) およびオキナガレガニPl. major(MacLeay, 1838) との識別形質も示した.Two grapsoid crabs, Pachygrapsus fakaravensis Rathbun, 1907, and Planes marinus Rathbun, 1914, are collected from the Okinawa Island Group, central Ryukyus, Japan. The former and the latter are recorded for the first time from Kouri Island and the Ryukyu Archipelago, respectively. Discriminative characters from their congeners, Pa. plicatus (H. Milne Edwards, 1837) and Pl. major (MacLeay, 1838), are also documented