The fourth Zoological Catalogue of Australia volume on Malacostracan Crustacea catalogues over 1200 species of amphipods (sea fleas, scuds and the beach and land hoppers), cumaceans and mysidaceans (opossum shrimps). This catalogue brings up-to-date the taxonomy of all known species in the Australian fauna and is particularly important for the cumacean and mysidacean faunas which have not been previously catalogued.