Okinawa Island, Central Ryukyus, Japan

The Okinawan terrestrial crab Geothelphusa tenuimanus is redescribed and its intraspecific variation is discussed. The geographically isolated Tam-agusuku (southern) population tends to have a more laterally-directed cur-vature of the anterolateral margins of the carapace and relatively shorter fourth ambulatory legs. However, these differences are not very significant and the diagnostic male first gonopod shows no differences. Therefore, all the populations on Okinawa Island are here regarded as conspecific. Habi-tats and morphological adaptations of the species are also discussed