J. Laurens Barnard

The Californian rocky intertidal, with its rich flora and its exposure to seas of normal salinity, supports a diverse and numerically abundant amphipodan fauna. Gammaridean Amphipoda are the most abundant of the macroscopic Crustacea in this zone; their density exceeds that the larger Decapoda and those companion orders of a similar body size such as Isopoda, Cumacea, and perhaps Tanaidacea.

Keys and diagnoses, with illustrations, to the families and genera of marine gammaridean Amphipoda are presented here in the form of a handbook. Since 1906 the number of families has been increased by 25 percent, the number of genera by 200 percent and the number of species by nearly 200 percent. At best, the present work is a stopgap. Specialists recognize that much exploration and discovery remain to be accomplished in the Amphipoda. No specialist is nearly satisfied with current classification at familial levels. Many genera are extremely confused, not only for the lack of clear description of their type-species but for the obviously erroneous inclusion of many of their congeners.

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.