Forty species are known, which, in their geographical distribution accompany, and are quite analogous to, the Chætodonts. One of the most common and most beautiful is called “Emperor of Japan” by the Dutch, which name has been adopted by Bloch for its specific designation, _Holacanthus imperator_. Its body is blue, longitudinally traversed by about thirty yellow bands; the ocular band, and the side behind the head, are black, edged with yellow; the caudal fin is yellow. It is a large species of this genus, sometimes attaining a length of 15 inches, and as an article of food is one of the most esteemed of all the Indian species. With regard to beauty of colours it is surpassed by another allied species, _H. diacanthus_, which likewise ranges from the east coast of Africa to Polynesia. POMACANTHUS differs from _Holacanthus_ in having from eight to ten spines only in the dorsal fin. The single species (_P. paru_) on which this genus is founded is one of the most common fishes of the West Indies, and offers one of the most remarkable instances of variation of colour within the limits of the same species: some specimens being ornamented with more or less distinct yellowish cross-bands, others with yellow crescent-shaped spots; in others black spots predominate. [Illustration: Fig. 170.--Scatophagus multifasciatus.] SCATOPHAGUS.--Two dorsal fins, united at the base, the first with ten or eleven spines; only the second is scaly. A recumbent spine before the dorsal, pointing forwards. Anal with four spines. Snout rather short. Præoperculum without spine. Scales very small. Four species are known, from the Indian Ocean, of which _S. argus_ is the most generally known, in fact, one of the most common Indian shore-fishes. It freely enters large rivers, and is said not to be particular in the selection of its food. The species figured (_S. multifasciatus_) represents _S. argus_ on the coasts of Australia. [Illustration: Fig. 171.--Bony enlargement of cranial bones of Ephippus. _a_, Enlargement of the frontal, and _b_, of the supraoccipital bones; _c_, interorbital septum; _d_, basis cranii. ⅓ nat. size.] EPHIPPUS.--Snout short, with the upper profile parabolic. Dorsal fin deeply emarginate between the spinous and soft portions, the former with nine spines, the third of which is rather elongate, and flexible; spinous portion not scaly; anal spines three. Pectoral fin short. Præoperculum without spine. Scales of moderate size, or rather small. Two or three species are known from the warmer parts of the Atlantic and Indian Oceans. The Atlantic species (_E. faber_) shows the remarkable peculiarity that in old specimens (12 and more inches long) the occipital crest, and sometimes some of the anterior neural and hæmal spines are enormously enlarged into a globular bony mass. This can hardly be regarded as a pathological change of the bone, as it has been found in all old specimens, without exception.