Relationships Within Eumalacostracan Crustacea

. A cladistic analysis was performed on 20 constituent higher taxa within the Eumala-costraca based on 3 1 characters of external anatomy. Variants of the most parsimonious scheme are presented, and the effects of tolerating different levels of uncertainty are evaluated. It is concluded that: 1) while the basic outline of Caiman's (1904) taxonomy of Eumalacostraca might be utilized, the arrangement within peracarids postulated by Siewing (1956) cannot be maintained; 2) the Baupldne approach of Schram (1981) has some merit and some of the controversial higher taxonomic groupings of eumalacostracan "orders" originally indicated by that method are vindicated; 3) the idea that the carapace is a derived feature within eumalacostracans, advanced by Dahl (1983), can be maintained only if a high level of homoplasy is tolerated; 4) the concept of a taxon Mysidacea seems best abandoned.