The species of Holacanthus, known as angel-fishes, are larger in size, and their colors are still more showy, being often scarlet or blue. In this genus the preopercle is armed with a strong spine, and there are fourteen or more strong spines in the dorsal. This genus has also its center of distribution in the East Indies, whence two species (septentrionalis and ronin) with concentric stripes of blue range northward to Japan. Holacanthus tibicen, jet-black with one yellow cross-band, is found from the Riu Kiu Islands southward. The angel-fish or isabelita (Holacanthus ciliaris), orange-red, sky-blue, and golden, as though gaudily painted, is the best-known species. The vaqueta de dos colores or rock beauty (Holacanthus bicolor), half jet-black, half golden, is scarcely less remarkable. Both are excellent food-fishes of the West Indies. Holacanthus passer is a showy inhabitant of the west coast of Mexico. Holacanthus diacanthus, orange, barred with blue, is one of the gaudiest inhabitants of the coral reefs of Polynesia. Holacanthus flavissimus, golden with some deep-blue markings, and Holacanthus nicobariensis, blackish with white circles, are found with other species in the same waters.
The genus Pomacanthus (Pomacanthodes) includes American species only, still larger in size and differing from Holacanthus in having nine to eleven spines only in the dorsal fin. The young of Pomacanthus are blackish, crossed by many curved yellow cross-bands, which disappear entirely with age. Three species are known, Pomacanthus arcuatus, the black angel, chirivita or portugais, Pomacanthus paru, the Indian-fish or paru of the West Indies, and Pomacanthus zonipectus, "Mojarra de las Piedras," of the west coast of Mexico. All are good food-fishes, but lacking the brilliant colors of Holacanthus and the fine pattern usual in Chætodon.
Fig. 341.—Rock Beauty, Holacanthus tricolor (L.). Puerto Rico.
The Pygæidæ.—Between the Chætodontidæ and the Acanthuridæ we would place the extinct family of Pygæidæ, of the Eocene. In Pygæus gigas and other species the dorsal spines are strong and numerous; there are 5 to 8 species in the anal fin, the scales are shagreen-like, and the teeth seem coarser than in the Chætodontidæ. The tail is apparently unarmed, and the soft dorsal, as in Chætodon, is much shorter than the spinous. To this family the Eocene genera, Aulorhamphus (bolceusis), with produced snout, and Apostasis (croaticus), with long spinous dorsal, probably belong.
Fig. 342.—The Moorish Idol, Zanclus canescens (Linnæus). From Hawaii. Family Zanclidæ. (Painting by Mrs. E. G. Norris.)
The Moorish Idols: Zanclidæ.—The family of Zanclidæ includes a single species, the Moorish idol or kihi kihi, Zanclus canescens. In this family the scales are reduced to a fine shagreen, and in the adult two bony horns grow out over the eye. The dorsal spines are prolonged in filaments and the color is yellow crossed by bars of black. Zanclus canescens is a very handsome fish with the general appearance and habit of a Chætodon, but the form is more exaggerated. It is found throughout Polynesia, from Japan to the off-shore islands of Mexico, and is generally common, though rarely entering rock pools.
Zanclus eocænus is recorded from the Italian Eocene.
The Tangs: Acanthuridæ.—In the next family, Acanthuridæ, the surgeon-fishes or tangs, the scales remain small and shagreen-like, the body is more elongate, the gill-openings still more restricted, and the teeth are flattened and incisor-like. The pubic bone is more elongate, and in all the species some sort of armature is developed on the side of the tail. The spinous dorsal in all is less developed than the soft dorsal. The species abound in the warm seas, especially about the tide pools, and are used as food. They undergo considerable changes with age, the caudal armature being developed by degrees. Nearly all are dull brown in color, but in some a vivid ornamentation is added. Fossil forms are found from the Eocene and later. Most of these are referable to Teuthis and Acanthurus.