KEY WORDS Crustacea, Decapoda, Brachyura, Portuninae, Miocene, Mahakamby, Madagascar.

org/10.5252/g2012n4a9 The small Mahakamby Island ( = Island of the Shrimp) is located in the Mo-zambique Channel (Indian Ocean) along the northwestern coast of the Ma-hajanga Province, (Soalala District, NW Madagascar). Miocene outcrops of Mahakamby were examined during the expeditions of two naturalists from the Muséum national d’Histoire naturelle, Paris: the first by Perrier de la Bâthie in 1915 and the second by Waterlot in 1922. Among the fossil invertebrates col-lected during the Waterlot’s Mission, some decapod crustaceans were partially reported by Collignon & Cottreau (1927) but their specimens are nowadays almost completely lost. However, additional materiel collected by Waterlot was rediscovered in the palaeontological collections of the Paris Museum. It al-lows a review and a discussion of the crustacean samples previously studied on the basis of iconographic material. Moreover, new specimens of brachyurans, collected during the Waterlot mission, are here assigned for the first time t