Redescription of (Dana, 1853) (Crustacea, Isopoda, Sphaeromatidae), designation of neotype, and 16S-rDNA molecular phylogeny of the north-eastern Pacific species.

(Dana, 1852) is revised, a male neotype is designated, photographed, and illustrated; the species occurs from Vancouver British Columbia to the central California coast. 16S-rDNA sequences (~650 bp) for all available ethanol preserved species of were used to hypothesize their relationships. Our analyses revealed a sister taxon relationship between the fully marine and the brackish to freshwater species, . The oyster associated and introduced is sister to a previously not recognized or identified, but genetically distinct, sp. collected at two sites in San Francisco Bay. sp. is probably also a western Pacific species based on its genetic relationship to . Photographic comparisons are offered for (marine), (freshwater), (introduced), sp. (presumably introduced), and (San Nicolas Island). Records of the holdings at the Los Angeles County Museum of Natural History are summarized. Without material available north of Vancouver through Alaska, the range of could not be genetically verified. This review includes a diagnosis and description of the genus Menzies, 1954.