Genus Eusyllis Malmgren, 1867

Type species: Eusyllis blomstrandi Malmgren, 1867 .

Diagnosis. Body relatively small to medium sized, with numerous segments. Dorsal ciliary bands in some species. Palps free or fused basally for short extension. Prostomium with four eyes, occasionally also two anterior eyespots, and three antennae. Nuchal organs as two semicircular, transverse rows of cilia on posterior border of prostomium, frequently extending along lateral margins. Peristomium with two pairs of peristomial cirri. Antennae, peristomial and dorsal cirri throughout smooth to irregularly articulated. Ventral cirri usually ovate to digitiform; ventral cirri of chaetiger 1 flattened, lamellar in some species. Compound chaetae as falcigers only, blades of variable lengths. Dorsal and ventral simple chaetae present at least on posterior parapodia. Pharynx straight, with mid-dorsal central tooth and trepan usually incomplete, with small denticles in ventral position (Brusa et al. 2013).

Remarks. The genus counts on 10 valid species (Brusa et al. 2013; Fukuda et al. 2015). This is the first record of the genus for the northeastern Brazilian coast.