A new deep-water lancelet (Cephalochordata) from off Cape Nomamisaki, SW Japan, with a proposal of the revised system recovering the genus Asymmetron.

Asymmetron inferum n. sp. is established for the holotype collected during the Hyper-Dolphin/Natsushima cruise in 2003 of the Japan Marine Science & Technology Center (JAMSTEC) off Cape Nomamisaki, southwestern end of Kagoshima Prefecture, at a depth of 229 m. A. inferum is very similar to its congener, A. lucayanum Andrews, 1893 (formerly called Epigonichthys lucayanus) but easily distinguishable from it by the larger number of total myotomes (83 in the former vs. 55-72 in the latter). The genus Asymmetron has been treated as a junior synonym of Epigonichthys, but is recovered as a valid genus distinct morphologically from another valid genus Epigonichthys (sensu stricto).