Review of Verrill, 1899 (Echinodermata, Ophiuroidea, Ophiacanthidae), description of new species in and , and new records from the Northwest Pacific and the South China Sea.

The ophiuroid genus is well characterized by the deep incisions in the disc. Prior to this study, it contained 32 accepted species, but species limits and geographic distributions were not well understood. The manned submersible vehicle 'Shenhaiyongshi' was used to collect ophiuroid specimens from the deep-sea seamounts and cold seeps in the South China Sea and Northwest Pacific at 602-3600 m depth, during 2018 to 2020. The genus was reviewed using both morphological data and a phylogenetic analysis, based on COI sequences. The taxonomic status of the genus Matsumoto, 1917, a junior homonym of Fitzinger, 1843 (a reptile) was clarified by proving prevailing usage of the ophiuroid name. A total of eight species were identified, including two new species, described as and , and two new records. The new species are characterized by unique features of the arm skeletons. Tabular keys to all and species are provided. Interspecific and intraspecific genetic distance of species ranged from 2.32% to 19.72%, and from 0.26% to 0.90%, respectively. The data suggest that species of the genus are more widely spread around the Northwest Pacific region deep-sea seamounts than previously known.