ABSTRACT. Keys, diagnoses and lists of species are presented for the marine families and genera of Gammaridea except those marinegammaroids treated by Barrtard& Barnard (1983). This work is a handbook for the identification of gammaridean amphipods to generic level through the use of artificial (non-phylogenetic) keys at the family-group level which lead to subsidiary keys to the genera of families or family groups. Genera in polytypic families are diagnosed and described sufficiently to fit the taxonomic complications within each group. Diagnoses of families are limited to those characters departing from a·gammaridean model which is diagnosed in words and illustrations; hence some families may have identical diagnoses. Therefore, cross-comparisons to similar families are made an organic part of each diagnosis. Family descriptions amplify the generalities of family characters. Relationships are identified not at phylogenetic level but in terms. of possible confusion in making identifications. The reader must cross-compare relationships among the several families that might be mentioned as part of the diagnoses because, to save space, all possible combinations are not replicated at every possible node. The same comparative method is generally but not exclusively used for the genera of each family. Multiple keys are provided for some of the more difficult families; taxa are often cited more tha, once in a key. A pictorial key to families operates with the same proviso that only the deviations from the model gammaridean are depicted. The pictorial key is arranged in reverse order so that the most anomalous taxa appear first and those closest to the model diagnosis are placed· at the end. This progression follows the idea that the most deviant taxa are the easiest to identify to family. level. The master key to families has the endpoints necessary to identify marine gammaroids by reference to Barnard & Barnard (1983); the two works are constructed .inparallel·fashion~·Families,andgenefawithin~families,areOfganisedalphabetically~·An index provides the principal reference for each genus and species. Where necessary, each taxon is supplied with notes on removals or major changes since 1965 which have not become common 2

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This part of the revision of the freshwater Gammarus species deals with the G. roeseli-group. Members of this artificial group are characterized by the presence of dorsal processes (carinae) on the metasome segments.

This third part of the revision of the freshwater Gammarus species deals with the G. balcanicus- group. Members of this artificial group are characterized by poorly setose pereiopods 3 and 4 and uropod 3 and by the absence of dorsal carinae (processes) on the metasome segments.