INTRODUCTION As a result of separate investigations on Panulirus japonicus (sens, lat.), the present authors independently came to the conclusion that more than one species was included under that name. The first author (George), when in 1958 studying specimens of the Western Australian spiny lobster which at that time was indicated by the name Panulirus longipes (A. Milne Edwards) (a species considered by many authors to be synonymous with P. japonicus), was dissatisfied with that identification and obtained material of the typical P. longipes from Zanzibar. Comparison with this material showed that the Western Australian spiny lobster represented an unnamed species, which he then described as P. cygnus. He also arrived at the conclusion that P. japonicus and P. longipes are separate species and that the latter perhaps should also be split up. The second author (Holthuis), during a year's visit (1952-1953) to the U.S. National Museum in Washington, D.C., was struck by the fact that the colour pattern of "Panulirus japonicus" from Hawaii is strikingly different from that of the typical Japanese P. japonicus, a difference that proved to be constant. He also found the colour pattern of P. longipes to be strikingly different from that of the typical P. japonicus, and further discovered constant morphological differences between the three forms, which convinced him that they represented three valid species. These finds were verified later with the collections of the Leiden Museum, where the types of P. japonicus are preserved; it was then decided to make a revision of the entire P. japonicus group. In the meantime E. P. Reed described a new species P. pascuensis from Easter Island, which also proved to belong