The lower jaw has a short sideways-projecting spine on either side near the tip.

This fish is a uniformly dark colour except for a row of light-coloured, opalescent scales along the belly.

Its range includes subtropical and tropical waters in the Indian and Pacific Oceans, and temperate, subtropical and tropical waters in the eastern Atlantic Ocean, from the Bay of Biscay southwards to Angola; it is absent from the western Atlantic.

It is generally a bathypelagic species, occurring at depths greater than 1,000 m (3,300 ft); its occasional capture between 425 and 525 m (1,400 and 1,700 ft) is indicative of a pattern of diurnal vertical migration.

[1] In a particularly warm period between 1996 and 2005, it was found at 320 metres (1,050 ft) off the coast of Greenland, well to the north of its normal range.