This edition represents the second edition of the list of decapod crustaceans and the first edition of the list of all other crustacean groups, including terrestrial, freshwater, and marine forms. The list has been greatly expanded to include more than 9,000 species from the United States (now including Hawaiian species) and Canada. Several detailed appendices have been added, including changes and additions to the entries for decapod crustaceans from the first edition and lists of endangered or threatened species, presumably extinct species, and nonindigenous species. The introduction is also expanded to include a detailed description of the diversity within the subphylum Crustacea.