The members of this genus (there are several), resemble the viperfish in their bulldog-shaped heads, with large mouth and long, fanglike teeth. But they do not have an adipose fin; the dorsal fin and the anal fin both stand far rearward close to the tail fin; the dorsal fin is even with the anal fin; and the first dorsal fin ray is not prolonged as it is in the viperfish. The chin bears a fleshy barbel nearly as long as the head and ending in a group of about three simple filaments. The sides of the body are clothed with about 6 rows of large, thin, somewhat irregular, hexagonal scales, and there is one row of luminescent spots low down along each side and two rows along the belly; also one small, circular light organ below each eye.
The tip of the lower jaw overlaps and encloses the tip of the upper jaw when the mouth is closed in the only member of the genus that has been reported from the Gulf of Maine (or is likely to be found there); the slender body is about 17 times as long as it is high; the ventral fins are only about as long as the head; the dorsal fin is of about the same size and shape as the anal fin, over which it stands; and there are about 85-86 light organs in each of the ventral rows, about 60 light organs in each of the lateral rows.
Black below as well as above, the sides with metallic iridescence.
This oceanic fish is so widespread in the northern North Atlantic that it was taken at almost all the stations that the Michael Sars occupied there in 1910, mostly between the 75 to 80 fathom level and the 410 fathom (750 meter) level, most plentifully at about 275 fathoms (500 meters). The early cruises of the Blake, and Albatross I took it at many localities also, along the continental slope of North America between the southeastern slope of the Newfoundland Banks and the Bahama Channel. Our only reason for mentioning it is that one specimen about 12 inches long (tip of snout to base of tail fin) was taken by a trawler on the northeastern part of Georges Bank (lat. 42°10' N., long. 67°05' W.), at about 100 fathoms, on January 20, 1936.