The decapod and stomatopod Crustacea of St Paul's Rocks

INTRODUCTION Saint Paul's Rocks (Penedos de São Pedro e São Paulo) are a small group of rocky islets on the mid-Atlantic ridge near the equator, occupying an area of roughly 250 by 425 m. There is no vegetation and, apart from birds and invertebrates, the islands are uninhabited. The Cambridge Expedition to Saint Paul's Rocks visited the group from 16 to 24 September 1979 and made extensive collections of the terrestrial and marine fauna; these included a number of Crustacea. The Decapoda and Stomatopoda of St Paul's Rocks are the subject of the present paper. Few detailed studies have been published to date on the Crustacea of St Paul's Rocks, largely because of the Rocks' remoteness and inhospitable nature. Crustacea, especially the common and conspicuous rock crab Grapsus grapsus, have been mentioned in several narratives and popular accounts, but the only material on which scientific reports have been based is that collected by H.M.S. "Challenger" in 1873. The Challenger reports mention eight species of Decapoda (5 Macrura, 1 Anomuran and 2 Brachyura) from St Paul's Rocks. The Cambridge Expedition collected nine species of Decapoda (2 Macrura and 7 Brachyura) and one species of Stomatopoda; in addition one macrurous decapod was observed but not collected. The total number of species of Decapoda now known from St Paul's Rocks amounts to fifteen (6 Macrura, 1 Anomuran and 8 Brachyura); Stomatopoda, not previously reported from the area, are represented by a single species. The following text assembles all the published and unpublished information known to us on the Decapoda and Stomatopoda of St Paul's Rocks. The abbreviations cb., cl., and tl. have been used for carapace width, carapace