A study of the extensive collection of calappid crabs made by the MUSORSTOM 9 expedition to the Marquesas Archipelago provided an opportunity to update and revise the list of species known from the islands and revealed a new species. Mursia poupini n. sp. is easily distinguished from the other Mursia species with crook-shaped second male pleopod (M. africana, M. flamma, M. microspina). M. poupini n. sp. differs from M. africana in its much shorter lateral spine; from M. flamma in the shape of the lower horizontal row on outer palmar face, and in lacking the sharply triangular teeth on posterior margin of carapace; from M. microspina in its longer lateral spine, in the shape of the lower horizontal row on outer palmar face, and in lacking the large oculus-shaped patch on inner palmar face.
Crustacea, Decapoda, Brachyura, Calappidae, Mursia, Pacific Ocean, Marquesas Islands, new species.