Salangathelphusa peractio, a new species of lowland freshwater crab from Pulau Langkawi, Peninsular Malaysia (Crustacea, Brachyura, Gecarcinucidae)

A new species of lowland freshwater crab of the family Gecarcinucidae, Salangathelphusa peractio, is described from Langkawi, an island off the northwestern coast of peninsular Malaysia. Salangathelphusa peractio sp. n. can be separated from S. brevicarinata (Hilgendorf, 1882) in having a proportionately broader external orbital tooth, a distinctly concave posterolateral margin, and the terminal segment of the male first gonopod is not distinctly bent laterally outwards; and from S. anophrys (Kemp, 1923) by its more quadrate carapace and the terminal segment of the male first gonopod possessing a relatively longer and less curved distal part. This is sixth wholly freshwater brachyuran species known from the island.