A new species, Careproctus ambustus, is described from 64 specimens based on evidence from morphological and molecular data. Specimens of Careproctus ambustus, new species, have been historically misidentified as the common Blacktail Snailfish, C. melanurus. The new species is distinguished from C. melanurus by its higher numbers of vertebrae (62–66 vs. 56–62 in C. melanurus), dorsal-fin rays (57–63 vs. 53–58), and anal-fin rays (51–55 vs. 46–51), and longer pelvic disc (14.1–21.2 vs. 12.6–20.7 % HL). In addition, the new species differs from C. melanurus by seven base pairs within a 492-base-pair region of the cytochrome oxidase c subunit 1 region, a 1.4% sequence divergence. Careproctus ambustus, new species, is found at depths of 58–1,172 m and ranges from Japan, through Alaska, to the west coast of Vancouver Island, British Columbia, where its distribution overlaps with C. melanurus, which ranges from southern Alaska and British Columbia to Baja California.
