In a series of studies on eunicids, there were explicit or implicit indications that Eunice riojai described from the north-western Caribbean Sea, and Eunice sebastiani described from south-east Brazil, were synonyms. This was based upon a then recent monograph on the genus, and on the fact that some specimens were found in drifting wood which would explain the large geographical range. The study of some large specimens of E. sebastiani, collected at the type locality, shows that there are several relevant morphological differences between the two species and thus both species names must be regarded as distinct. In fact, E. sebastiani is unique in the genus because their maxillae V are bidentate. Furthermore, herein we re-describe these two species and re-evaluate some morphological features described in previous studies.
