Remarks. The genus Perkinsiana was established by Knight-Jones (1983), in order to accommodate species previously assigned to the genera Demonax Kinberg, 1867 (= Parasabella fide Tovar-Hernández & Harris 2010), Potamilla Malmgren, 1866, and Potamethus Chamberlin, 1919. Fitzhugh (1989) provided a diagnosis slightly modified from that of Knight-Jones (1983) and indicated the genus was not united by any recognized synapomorphies, Capa (2007) amended the genus and, based on a cladistic analysis, she concluded that Perkinsiana is paraphyletic. Tovar-Hernández et al. (2012) amended the generic diagnosis of Perkinsiana, to include the presence of a palmate membrane and radiolar flanges, and three patterns of abdominal notochaetae: type A) chaetae with a broad hood, progressively tapering to distal tips in all chaetigers; type B) with a broad knee, distal ends narrowing abruptly on all chaetigers; and type C) elongate, with a narrow hood.
In this study, Perkinsiana antarctica (Kinberg, 1867) and Perkinsiana assimilis (McIntosh, 1885) are redescribed and reported for several localities off Uruguay, Argentina and Chile. Sabella magalhaensis Kinberg, 1867 is transferred to Perkinsiana, and P. littoralis Hartman, 1967 is synonymized to it. Perkinsiana antarctica was found in intertidal zones; P. assimilis, from 90–500 m depth, and P. magalhaensis, from 3–20 m depth. Six species of Perkinsiana from South America are currently valid (Table 2).