A slim-bodied shark with a short, blunt snout and a long, narrow tail, the green lanternshark attains a maximum known length of 26 cm (10 in). The eyes are very large and oval in shape. The nostrils are preceded by short skin flaps. There are 29–34 tooth rows in the upper jaw, each tooth with a narrow central cusp flanked by fewer than three pairs of lateral cusplets. The lower jaw contains 24–32 tooth rows, their bases interlocking to form a continuous cutting surface and each tooth bearing a horizontal narrow cusp. The five pairs of gill slits are very short, comparable to the spiracle in size.
The first dorsal fin bears a spine in front and originates over the trailing margin of the broad and rounded pectoral fins. The second dorsal fin also bears a spine in front and is over twice as large as the first in area, with the span between it and the first dorsal fin approximately equal to the distance between the snout tip and first gill slit. The anal fin is absent. The caudal fin is low and narrow, with an indistinct lower lobe and an upper lobe about as long as the head. The dermal denticles on the sides of the body are stout and thorn-shaped, widely spaced without any regular pattern; the snout is mostly covered by denticles. The dorsal coloration is dark brown to gray; the undersides of the body and snout are black, with a broad, black marking above and behind each pelvic fin, and thin, black marks on the tail. These black markings contain numerous light-emitting photophores.
This largely bottom-dwelling species has been caught at depths of 196–915 m (643–3,002 ft), with most individuals being found deeper than 350 m (1,150 ft).
Green lanternsharks feed mainly on squid and octopus, and are frequently found with cephalopod eyes and beaks in their stomachs so large that the sharks would have had to distend their jaws considerably to swallow them.