Ambassis.—Body short, strongly compressed, covered with large thin deciduous scales. Mouth oblique, with the lower jaw longest; teeth villiform, without conspicuously larger canines; teeth on the vomer and palatine bones. Two dorsal fins, the first with seven, the anal with three spines; a horizontal spine pointing forwards in front of the dorsal fin. The lower limb of the præoperculum with a double serrated margin.
This genus comprises the smallest of all Percoids, some of the species not much exceeding one inch in length. They are most abundant on the coasts of the tropical Indo-Pacific, and in the fresh waters belonging to that area. The species are numerous (some thirty having been described), and very difficult to distinguish. Their coloration is very plain, a silvery hue prevailing over the whole fish.
Apogon.—Body rather short, covered with large deciduous scales. Mouth oblique, with the lower jaw longest; teeth villiform, without canines; teeth on the vomer and palatine bones. Two dorsal fins, the first with six or seven, the anal with two spines. Præoperculum with a double edge on the margin, one or both edges being serrated. Seven branchiostegals.
Fig. 166.—Apogon frenatus.
Although of similarly small size, the fishes of this genus represent a more highly developed form of the Percoid type than Ambassis. Their distribution coincides very much with that of Ambassis, but they are chiefly marine, comparatively few of the species entering fresh water. They belong to the kind of fishes which, from their habit, are termed “Coral Fishes,” being found in greatest abundance on, or in the neighbourhood of, coral reefs, in company with Chætodonts, Pomacentridæ, and others. Their colours also are ornamental and highly diversified, as is generally the case in coral fishes, the majority of the species showing transverse or longitudinal bands or large spots, and numerous other smaller markings which, in the dead fish, soon disappear. Nearly one hundred species have been described, of which a few only occur in the Atlantic, one extending northwards into the Mediterranean.
Chilodipterus, Acropoma, and Scombrops are allied genera, but with canine teeth in one or both jaws.
Pomatomus.—Body oblong, covered with scales of moderate size. Eye very large. All the teeth villiform, without canines; teeth on the vomer and palatine bones. Two dorsal fins, the first with seven, the anal with two spines. No serration on any of the bones of the head. Branchiostegals seven.
One species only is known, P. telescopium, which grows to a length of nearly two feet. It is not uncommon in the Mediterranean and neighbouring parts of the Atlantic, but only occasionally caught, as it lives habitually at a greater depth than any other Percoid as far as is known at present, probably at depths from 80 to 200 fathoms; a habit sufficiently indicated by its exceedingly large eye.
Priacanthus.—Body short, compressed, covered with small rough scales, which extend also over the short snout. Lower jaw and chin prominent. Eye large. All the teeth villiform, without canines; teeth on the vomer and palatine bones. One dorsal fin with ten spines, anal with three. Præoperculum serrated, with a more or less prominent, flat, triangular spine at the angle.