I. Anal not exactly opposed to the rayed dorsal, or much longer than the latter; no hyoid barbel.
A. Rayed dorsal far forward, between pectorals and ventrals; pectorals well developed (Chauliodontinae). Chauliodus.
B. Rayed dorsal above or behind the ventrals; pectorals well developed.
1. Body more or less elongate; ventrals well developed (Gonostomatinae).
a. A hyoid barbel. Astronesthes.
b. No barbel. Bathylychnus, Gonostoma, Cyclothone, Triplophos, Photichthys, Bathylaco, Diplophos, Maurolicus, Ichthyococcus.
2. Body short and deep; ventrals rudimentary or absent (Stenoptychinae). Argyropelecus, Sternoptyx, Polyipnus.
II. Dorsal and anal opposed to each other and very far back on the caudal region; pectorals often reduced or absent; hyoid barbel often present. (Stomiatinae). Stomias, Macrostomias, Echiostoma, Opostomias, Pachystomias, Photonectes, Malacosteus, Thaumatostomias, Photostomias.
This family, comprising about 55 species, has a world-wide distribution, but most of the known forms have been obtained from the Atlantic; some of the species occur both in the Atlantic and the Indo-Pacific. Chauliodus, Astronesthes, and Stomias are among the fishes with the most formidable dentition.
Fam. 20. Gonorhynchidae.—Margin of the upper jaw formed by the praemaxillaries and the maxillaries, the latter articulated above the former to the ethmoid. Supraoccipital in contact with the frontals, widely separating the small parietals; opercular bones well developed; symplectic present. Basis cranii simple. Mouth small and toothless, inferior, surrounded by thick, fringed lips. Four branchiostegal rays. Head and body entirely covered with small spiny scales. Praecaudal vertebrae with strong parapophyses, to the extremity of which slender ribs and epipleurals are attached. No postclavicle. Pectoral fins inserted low down, folding like the ventrals; latter with 10 rays.