Psettus.—Body much compressed and elevated; snout rather short. One dorsal, entirely covered with scales, with seven or eight spines; anal fin with three. Ventrals very small, rudimentary. Teeth villiform; no teeth on the palate. Scales small, ctenoid.
Only three species are known; one, P. sebæ, from the west coast of Africa, the two others from the Indo-Pacific. P. argenteus is a very common fish, attaining to a length of about 10 inches.
Fig. 199.—Psettus argenteus.
Platax.—Body much compressed and elevated; snout very short. One dorsal, with the spinous portion nearly entirely hidden, and formed by from three to seven spines; anal with three. Ventrals well developed, with one spine and five rays. Teeth setiform, with an outer series of rather larger teeth, notched at the top; palate toothless. Scales of moderate size or rather small.
These fishes are called “Sea-bats,” from the extraordinary length of some portion of their dorsal and anal fins and of their ventrals. These long lobes are generally of a deep black colour. In mature and old individuals the fin-rays are much shorter than in the young, which have been described as distinct species. There are probably not more than seven species of “Sea-bats,” if so many, and they all belong to the Indian Ocean and Western Pacific, where they are very common.
Zanclus.—Body much compressed and elevated. One dorsal, with seven spines, the third of which is very elongate. No teeth on the palate. Scales minute, velvety.
One species (Z. cornutus), which is extremely common in the Indo-Pacific. It is easily recognised by its snout, which is produced like that of Chelmon, and by the broad black bands crossing the yellow ground-colour. It attains to a length of eight inches, and undergoes during growth similar changes as Acanthurus.
Anomalops.—Body oblong, covered with small, rough scales. Snout very short, convex, with wide cleft of the mouth. Eyes very large; below the eye, in a cavity of the infraorbital ring, there is a glandular phosphorescent organ. Villiform teeth in the jaws and on the palatine bones, none on the vomer. First dorsal fin short, with a few feeble spines connected by membrane.
This genus, of which one species only is known (A. palpebratus), represents the family of Horse-Mackerels in the depths of the sea; but we do not know, at present, at what depth it lives. Only six specimens have been obtained hitherto from the vicinity of Amboyna, the Fidji, and Paumotu Islands; the largest was twelve inches long.