One family only belongs to this division.
Family—Berycidæ.
Body short, with ctenoid scales, which are rarely absent. Eyes lateral, large (except Melamphaës). Cleft of the mouth lateral, oblique; jaws with villiform teeth; palate generally toothed. Opercular bones more or less armed. Eight (four) branchiostegals.
This family offers several points of biological interest. All its members are strictly marine; but only two of the genera are surface-forms (Holocentrum and Myripristis). All the others descend considerably below the surface, and even some of the species of Myripristis habitually inhabit depths of from 50 to 100 fathoms. Polymixia and Beryx have been found in 345 fathoms. Melamphaës must live at a still greater depth, as we may infer from the small size of its eye; this fish is not likely to come nearer to the surface than to about 200 fathoms. The other genera named have extremely large eyes, and, therefore, may be assumed to ascend into such superficial strata as are still lit up by a certain proportion of sun-rays. The highly-developed apparatus for the secretion of superficial mucus, with which these fishes are provided, is another sign of their living at a greater depth than any of the preceding families of Acanthopterygians. In accordance with this vertical distribution, Berycoid fishes have a wide horizontal range, and several species occur at Madeira as well as in Japan.
Fossil Berycoids show a still greater diversity of form than living; they belong to the oldest Teleosteous fishes, the majority of the Acanthopterygians found in the chalk being representatives of this family. Beryx has been found in several species, with other genera now extinct: Pseudoberyx, with abdominal ventrals, from Mount Lebanon; Berycopsis, with cycloid scales; Homonotus, Stenostoma, Sphenocephalus, Acanus, Hoplopteryx, Platycornus, with granular scales; Podocys, with a dorsal fin extending to the neck; Acrogaster, Macrolepis, and Rhacolepis, from the chalk of Brazil. Species of Holocentrum and Myripristis occur in the Monte Bolca formation.
Monocentris.—Snout obtuse, convex, short; eye of moderate size. Villiform teeth on the palatine bones, but none on the vomer. Opercular bones without armature. Scales very large, bony, forming a rigid carapace. Ventrals reduced to a single strong spine and a few rudimentary rays.
Fig. 183.—Monocentris japonicus.
One species only is known (M. japonicus) from the seas off Japan and Mauritius. It does not attain to any size, and is not common.
Hoplostethus.—Snout very short and obtuse; eye large. Villiform teeth on the palatine bones, but none on the vomer. Operculum unarmed, a strong spine at the scapulary and the angle of the præoperculum. Scales ctenoid, of moderate size; abdominal edge serrated. One dorsal, with six spines; ventrals with six soft rays; caudal deeply forked.