This work deals with 31 species of Sicyonia H. Milne Edwards, 1830, based on the collections made by the IRD (ex ORSTOM) and the Muséum national d'Histoire naturelle, Paris, and on the collections of 28 other museums. Nineteen species are considered valid: S. australiensis Hanamura & Wadley, 1998; S. benthophila de Man, 1907; S. bispinosa de Haan, 1850; S. curvirostris Balss, 1913; S. fallax de Man, 1907; S. furcata Miers, 1878; S. inflexa (Kubo, 1949); S. japonica Balss, 1914; S. laevis Bate, 1881; S. lancifer (Olivier, 1811); S. longicauda Rathbun, 1906; S. nasica Burukovsky, 1990; S. ocellata Stimpson, 1860; S. parafallax Crosnier, 1995; S. parvula de Haan, 1850; S. rectirostris de Man, 1907; S. trispinosa de Man, 1907; S. truncata (Kubo, 1949) and S. vitulans (Kubo, 1949). Four species are considered to be syn-onyms: S. cristata (de Haan, 1844) = S. lancifer; S. formosa (Chan & Yu, 1985) = S. furcata; S. ommanneyi Hall, 1961 = S. ocellata; S. nebulosa Kubo, 1949 = S. laevis. Twelve species are described as new: S. abathophila n. sp., S. adunca n. sp., S. altirostrum n. sp., S. dejouanneti n. sp., S. komai n. sp., S. longicornis n. sp., S. metavitulans n. sp., S. parajaponica n. sp., S. robusta n. sp., S. rocroi n. sp., S. rotunda n. sp. and S. taiwanensis n. sp. Some forms, near S. australiensis and S. dejouanneti n. sp., are mentioned but not named because the material available is insufficient. An attempt is made to classify the Indo-West Pacific species of Sicyonia into eight groups. Some groups are coherent, while others are certainly artificial. Some species cannot be placed in any of the groups and the placement of several species known from one sex only remains hazardous. An identification key is presented. Particular care was taken in illustrating the genitalia, which provide the most important characters for recognizing the species. Colour photographs show the coloration of living specimens of 17 species. Depth zones and geographic distributions of all the species are presented in tabular form. As with previous studies, high species diversity of the Philippines-Indonesia fauna is evident, as well as the reduction of the number of species when one moves away from the area, except for New Caledonian area because of the unusually high density of the samples collected in this area.
Crustacea, Decapoda, Penaeoidea, Sicyoniidae, Sicyonia, revision, Indo-West Pacific, new species.