Abstract
A new species of Poecilochaetus (Polychaeta: Poecilochaetidae) is described from coastal waters off Southern California. Much of the material was collected as part of the benthic infaunal survey work carried out by the Sanitation Districts of Los Angeles County as part of their ocean monitoring program. Numerous specimens of this new species have also been collected throughout the Southern California Bight during U.S. Environmental Protection Agency (EPA) regional surveys in 1994, 1998, and 2003. The distinct characters of this new species were first noted three decades ago, but a formal description was never published. These specimens have been reported frequently in survey data under the provisional name Poecilochaetus sp. A. The number of branchial filaments, the location of these filaments along the body, and the absence of a middorsal chitinous plate on setiger 9 make Poecilochaetus martini sp. nov. unique. This new species also has elongated interramal papillae on the branchiate setigers, a character only recently noted. P. martini sp. nov. is compared to other branchiate species in the genus that also have interramal structures.