Two of the species of Pectinariidae previously reported from the Brazilian coast are herein described, together with a new species and also new record for the genus Petta Malmgren, 1866 for the southern Atlantic. Amphictene catharinensis (Grube, 1870) was described from material from off Santa Catarina, southern Brazil, but the most recent description for these animals comes from Nilsson (1928); a redescription for A. catharinensis is herein provided. Pectinaria nonatoi n. sp. was informally described as P. (Pectinaria) laelia nomen nudum in an unpublished thesis and a formal description has never been provided, although the species has been reported from several other localities off the Brazilian shoreline, mostly in ecological studies; the species is formally described herein and compared to the most similar congeners. Petta alissoni n. sp. is also described and compared to the most similar congeners and this is the first record for animals of this genus from southern Atlantic. There are also records for Pectinaria gouldii (Verrill, 1874) and P. regalis Verrill, 1901 from off the Brazilian coast, and a doubtful record for Lagis pseudokoreni (Day, 1955), but we did not find any material belonging to those taxa.
Keywords: Annelida, “Polychaeta”, Amphictene, Pectinaria, Petta, taxonomy, new species.