Hymenocephalus aterrimus Gilbert 1905

This species is distinguished by the following characters: a black-colored large-headed fish, with head size 21-25% TL; pelvic fin rays 13-14; pectoral fin rays 13-16; projecting snout, 20-24% HL; head bones are papery thin and often distorted; no barbel; small orbit diameter, 20-24% HL; interorbital width 60-70% HW; infraorbital width 20-25% HL; postorbital-preopercular interspace 10-14% HL; preopercular supporter is very small and forked; gill rakers 21-25; ventral striae reaching to about ? from pelvic fin bases to periproct; small otolith with rounded outline, no predorsal lobe developed; colliculi separated; otholith length to height (OL:OH), 1.0-1.2; total colliculum length to pseudocolliculum length (TCL:PCL) is 2.2-2.8 (Ref. 98298).

Found on the continental slope (Ref. 75154). Benthopelagic (Ref. 58302).