Four specimens (53.4–67.2 mm in standard length) of the genus Bolinichthys Paxton, 1972, caught off Fukushima Prefecture (Pacific coast of Tohoku District) and the Ogasawara Islands, were identified as Bolinichthys pyrsobolus (Alcock, 1890) from the following characters: 12 pectoral-fin rays; Vn at anterior border of eye, between nasal rosette and anterior edge of pupil; post-ocular photophores absent; distance between PVO1 and PVO2 less than that between Op1 and Op2; VLO slightly higher than midway between lateral line and pelvic-fin base; VO2 highly elevated, located near the line connecting PO4 and SAO1; infracaudal luminous gland reaching slightly ahead of AOp3; no luminous patches on dorsal and pelvic-fin bases; 3 or 4 luminous patches along the anal-fin base; and ventral edge of interopercle smooth. Although the number of gill rakers, one of the diagnostic characters of the species, had been previously established as 5 or 6 + 1 + 10–13 = 17–20, it was 7 + 1 + 14 = 22 in one of the present specimens, a difference regarded here as intraspecific variation only, due to similar variation in congeners. Other characters in the specimen were closely consistent in the remaining three specimens. Multiple occurrences of B. pyrsobolus in Japanese waters have been recorded previously, but without clear evidence of correct identification. Accordingly, the present specimens represent the first reliable records of B. pyrsobolus from Japanese waters, that off Minamisouma, Fukushima Prefecture being the northernmost for the species. Supracaudal and infracaudal luminous glands and luminous patches along the anal-fin base of one of the present specimens fluoresced distinctly light green under ca. 365 nm ultraviolet light, while fresh (before freezing). The new Japanese standard name “Hoshizora-mikazukihadaka” is proposed for the species.
