A new species of amphinomid polychaete, Benthoscolex seisuiaesp. n., is described from the Sea of Kumano, Japan, from depths of 487-596 m. The species is distinguishable from its congeners by the following features: i) palps 1.8 times as long as lateral antennae; ii) branchiae do not reach to the tip of the notochaetae. This is the first record of Benthoscolex from Japan. A partial mitochondrial cytochrome c oxidase subunit I gene sequence from the holotype of B. seisuiaesp. n. is provided for reliable species identification in the future.
Keywords: Amphinomida; Polychaeta; deep sea; new genus record; polychaetes; taxonomy.