Introduction: Brazil has more than 8 000 km of coastline but its marine invertebrates are still poorly known. The cirratulid polychaetes have been an especially neglected group because of its challenging taxonomy. Objective: to describe a new species of Protocirrineris. Methods: In a recent survey in two of the largest Brazilian bays, Todos os Santos Bay and Camamu Bay, 84 specimens of four morphotypes of the multitentaculate genus Protocirrineris were collected. Because of the lack of modified chaetae, the taxonomy of Protocirrineris is challenging and only two of these morphotypes are herein described as new species. Results: These two new species are characterized by having tentacular filaments in two groups over chaetigers 3-4 and first branchiae present from chaetiger 1. They differ from each other in relation to the nature of the achaetigerous region, posterior region, ultrastructure of capillary chaetae and methyl green staining pattern. Two incomplete specimens are also considered as Protocirrineris, and brief descriptions are given. Conclusions: The genus Protocirrineris is cited for the first time in Brazil. Four new morphotypes were found in two large estuaries of Brazil, and two new species are formally described.

Keywords: Taxonomy, Protocirrineris, new species, Todos os Santos Bay, Camamu Bay, Northern Brazil.