Description of sp. nov. From Japan (Annelida: Hesionidae) and A Redescription of (Wesenberg-Lund, 1950) and Its Confirmation Within Hesionini.

sp. nov. is newly described based on specimens collected in Sagami Bay, Japan, at a depth of 150-250 m. This new species resembles (Wesenberg-Lund, 1950) from Iceland, but differs because in sp. nov. the ventral cirri surpass the tips of the neurochaetal lobes, reaching to the medial part of the neurochaetal bundle; the palps are 1/2-4/5 as long as the antennae; the aciculae are pale brownish; and the dorsal integument shows 9-10 transverse wrinkles per segment, whereas in the ventral cirri hardly reach the tips of the neurochaetal lobes; the palps are as long as the antennae; the aciculae are black; and there are 15 transverse wrinkles per segment. A morphological redescription of based on its type material and a revised key to identify species in the genus are also provided. A phylogenetic analysis based upon four genes (COI, 16S, 18S, 28S) confirms its position within Hesionini.