Description of a new species of freshwater crab of the genus rcithelphusa Pati & Sudha Devi, 2015 (Decapoda: Brachyura: Gecarcinucidae) from the Western Ghats, Kerala, India.

A new species of the hitherto monotypic gecarcinucid freshwater crab genus, Arcithelphusa Pati Sudha Devi, 2015, is described from the Western Ghats, in the Wayanad district of Kerala, India. Arcithelphusa tumpikkai sp. nov. can be easily distinguished from the only congener, A. cochleariformis Pati Sudha Devi, 2015, mainly by its relatively broader carapace, the presence of a short flagellum on the exopod of the third maxilliped, and the relatively less stout male first gonopod, with a sharply bent and relatively long terminal segment. The diagnosis for Arcithelphusa is emended to include the new species, which can be useful in distinguishing it from the closely related genus Cylindrotelphusa Alcock, 1909. The state of Kerala now has 38 species of gecarcinucid crabs, including the present new species.