[Garman, Mem. Mus. Compar. Zoology, vol. 24. 1899, p. 246, pl. J, fig. 3.]
The general aspect of cyclothone is extremely characteristic, the somewhat compressed body being deepest at the gill opening with the upper surface of the head concave in profile, the mouth so large that it gapes back of the eye, the lower jaw projecting, the eye very small, and the gill openings very long. The dorsal fin stands over the anal (the latter is much the longer of the two), both originating close behind the middle of the body. The caudal fin is deeply forked and there is no adipose fin.
The luminescent spots are arranged as follows: One on the head; 1 close below the eye and in front of it; 2 on each gill cover; 9 or 10 between the branchiostegal rays; 2 longitudinal rows along each side of the body, a lower row of 13 from throat to ventral fins, 4 from ventrals to anal fin, and 13 from anal to caudal, and an upper row of 7 reaching about as far back as the ventrals.
Cyclothone signata is colorless or pale gray, except that the blackish, dark silvery lining of the abdominal cavity shows through, that the luminous organs are black rimmed and silver centered, and that there are the following black markings: a Y-shaped mark on the forehead; a series of spots or short transverse stripes on the flank; spots between the bases of the dorsal and anal fin rays; one or two transverse streaks across the bases of the caudal fin rays; and a number of [page 147] irregular flecks and dots along the back and on the gill covers.
This is an oceanic fish, very abundant in temperate latitudes in the Atlantic where it lives pelagic from about 100 fathoms down to 250 fathoms; hundreds have often been taken in a single haul. It is also known from the Pacific.
Cyclothone appears within our limits only as a stray from the Atlantic Basin; one 23 mm. long that we took in a haul from 30 fathoms on Browns Bank, June 24, 1915, and a second mutilated specimen probably of this species from the Fundy Deep (haul from 90 fathoms), March 22, 1920, are the only definite records of it within our limits.
 For detailed accounts and colored illustrations see Garman (Mem. Mus. Comp. Zool., vol. 24, 1899, p. 246, pl. J, fig. 3), Brauer (Wissensch. Ergeb. Deutschen Tiefsee-Exped. (1898-1899), 1906, vol. 15, Pt. 1, p. 77, pl. 6, fig. 6), Murray and Hjort (Depths of the Ocean, 1912, pl. I).