Geosesarma wongi sp. nov., a distinctive new species of semiterrestrial crab from Tapah Hills in Perak, Peninsular Malaysia; with notes on G. peraccae (Nobili, 1903) and G. cataracta Ng, 1986 (Crustacea, Brachyura, Sesarmidae)

A new species of semiterrestrial freshwater crab is described from Tapah Hills in Peninsular Malaysia. <i>Geosesarma wongi</i> <b>sp. nov.</b> is the 13^th member of the genus reported from the country and is most similar to <i>G. peraccae</i> (Nobili, 1903) and <i>G. cataracta</i> Ng, 1986, but easily separated by its distinct carapace features and structures of the adult male chela and male first gonopod. The types of <i>G. peraccae</i> are figured for the first time. <i>Geosesarma cataracta</i> is also figured in detail, and the type series is shown to be mixed.