The Damsel-fishes: Pomacentridæ.—The Pomacentridæ, called rock-pilots or damsel-fishes, are exclusively marine and have in all cases but two anal spines. The species are often very brilliantly colored, lustrous metallic blue and orange or scarlet being the prevailing shades among the bright-colored species. Their habits in the reef pools correspond very closely with those of the Chætodontidæ. With the rock-pilots, as with the butterfly-fishes, the exceeding alertness and quickness of movement make up for lack of protective colors. With both groups the choice of rocky basins, crevices in the coral, and holes in coral reefs preserves them from attacks of enemies large enough to destroy them. In Samoa the interstices in masses of living coral are often filled with these gorgeous little fishes. The Pomacentridæ are chiefly confined to the coral reefs, few ranging to the northward of the Tropic of Cancer. Sometimes the young are colored differently from the adult, having sky-blue spots and often ocelli on the fins, which disappear with age. But one species Chromis chromis, is found in the Mediterranean. Chromis punctipinnis, the blacksmith, is found in southern California, and Chromis notatus is the common dogoro of Japan. One of the largest species, reaching the length of a foot, is the Garibaldi, Hypsypops rubicundus, of the rocky shores of southern California. This fish, when full grown, is of a pure bright scarlet. The young are greenish, marked with blue spots. Species of Pomacentrus, locally known as pescado azul, abound in the West Indies and on the west coast of Mexico. Pomacentrus fuscus is the commonest West Indian species, and Pomacentrus rectifrenum the most abundant on the west coast of Mexico, the young, of an exquisite sky-blue, crowding the rock pools. Pomacentrus of many species, blue, scarlet, black, and golden, abound in Polynesia, and no rock pool in the East Indies is without several forms of this type. The type reaches its greatest development in the south seas. About forty different species of Pomacentrus and Glyphisodon occur in the corals of the harbor of Apia in Samoa.
Fig. 315.—Cockeye Pilot, Glyphisodon marginatus (Bloch). Cuba.
Almost equally abundant are the species of Glyphisodon. The "cockeye pilot," or jaqueta, Glyphisodon marginatus, green with black bands, swarms in the West Indies, occasionally ranging northward, and is equally common on the west coast of Mexico. Glyphisodon abdominalis replaces it in Hawaii, and the Asiatic Glyphisodon saxatilis is perhaps the parent of both. Glyphisodon sordidus banded with pale and with a black ocellus below the soft dorsal is very common from Hawaii to the Red Sea, and is a food-fish of some importance. Glyphisodon cœlestinus blue, with black bands, abounds in the south seas.
The many species of Amphiprion are always brilliant, red or orange, usually marked by one or two cross-bands of creamy blue. Amphiprion melanopus abounds in the south seas. Azurina hirundo is a slender species of lower California of a brilliant metallic blue. All these species are carnivorous, feeding on shrimps, worms, and the like.
Fig. 316.—Indigo Damsel fish, Microspathodon dorsalis (Gill). Mazatlan, Mex.
Microspathodon is herbivorous, the serrated incisors being loosely implanted in the jaws. Microspathodon dorsalis, of the west coast of Mexico, is of a deep indigo-blue color, with streamer-like fins. Microspathodon chrysurus, of the West Indian coral reefs, black with round blue spots and the tail yellow. This family is probably of recent origin, as few fossils are referred to it. Odonteus pygmæus of the Eocene perhaps belongs to it.
Suborder Pharyngognathi.—The wrasses and parrot-fishes, constituting the group called Pharyngognathi (φαρύγξ, gullet; γνάθος, jaw), by Johannes Müller, have the lower pharyngeal bones much enlarged and solidly united, their teeth being either rounded or else flat and paved. The nostrils, ventral fins, pectoral fins and shoulder-girdle are of the ordinary perch-like type. The teeth are, however, highly specialized, usually large and canine-like, developed in the jaws only, and the gills are reduced in number, 3½ instead of 4, with no slit behind the last half gill. The scales are always cycloid and are usually large. In the tropical forms the vertebræ are always twenty-four in number (10 + 14), but in northern forms the number is largely increased with a proportionate increase in the number and strength of the dorsal spines. All the species are strictly marine, and the coloration is often the most highly specialized and brilliant known among fishes, the predominant shade being blue.
