Hymenocephalus lethonemus Jordan and Gilbert 1904

Hymenocephalus lethonemus Jordan and Gilbert, 1904:615, text-fig. (holotype, USNM 50936; Sagami Bay, Japan, 120–265 fm [219–485 m]; paratypes, CAS-SU 8641 [3 spec.], USNM 51455 [3 spec.]).— Gilbert and Hubbs, 1916:188–189 (22 spec., s. Japan, East China Sea, 197–440 fm [360–805 m]).— Okamura, 1970:54–56, pl. II, text-fig. 23 (83 spec., 85–140 mm TL; e. coast of s. Japan).— Yatou in Okamura et al., 1982:143, 347, fig. 87 (p. 142) (7 spec., 175. 5–233 mm TL; Kyushu-Palau Ridge).— Okamura in Masuda et al., 1984:94, pl. 80–G (compiled).— Okamura in Okamura and Kitajima, 1984:201, 358, fig. 142 (p. 200) (8 spec., 148–180 mm TL; East China Sea [Okinawa Trough]; 570–810 m).— Chiou et al., 2004b:44, fig. 12 (13 spec., ne. Taiwan).— Shao et al., 2008: table 2 (21 spec., Taiwan [NET, SWT, SCS], 441–1040 m).

MATERIAL EXAMINED (36 spec.).— NET: ASIZP 61231 (1, 126 TL), Da-xi; ASZIP 64270 (2, 105+-108+ TL), CP 234, 547 m; ASZIP 66974 (12, 112–124 TL), Da-xi . SWT: ASIZP 65561 (1, 120+ TL) and ASIZP 65611 (1, 115 TL), CD 203, 634– 866 m; ASIZP 65598 (3, 120–155 TL), CD 138, 441 m; ASIZP 65604 (1, 133 TL) and ASIZP 66946 (1, 330 TL), CD 134, 736– 1040 m; ASIZP 66731 (1, 97 TL), OCP 317, 515 m; ASIZP 66871 (5, 43–68 TL), OCP 312, 517 m; ASIZP 66872 (1, 78 TL), CD 311, 516 m; ASIZP 66873 (4, 50–80+ TL), OCP 313, 516 m; ASIZP 67582 (2, 75+-95+ TL), CP 348, 395 m. Other specimens: ASIZP 67976 (1, 151 TL), Aurora .

DISTINGUISHING FEATURES.— 1D II 9–11; P i13–i16; V 11 (rarely12); inner GR-I 21–25 total; pyl. caeca 11–16. Head about 5–6 in TL; body depth about 8.0–9.5 TL. Snout high, pointed; mouth large, upper jaw extending posteriorly to below hind margin of orbit; barbel absent; gill openings wide, gill membrane free over isthmus; outer gill slit about as wide as orbit. Attains about 180 mm TL. (Compiled from Okamura [1970] and Gilbert and Hubbs [1916]).

DISTRIBUTION.— Pacific coast of s. Japan, East China Sea off Kyushu Is., Japan, and Taiwan (NET, SWT, SCS), in 360–1040 m.

REMARKS.— Okamura (1970:56) noted that among members of Hymenocephalus, this is the deepest-occurring in Japan.