Seventy species are known from the tropical parts of the Atlantic and Indo-Pacific, nearly all being beautifully ornamented with bands or spots. Of the ornamental markings a dark or bicoloured band, passing through the eye and ascending towards the back, is very generally found in these fishes; it frequently occurs again in other marine Acanthopterygians, in which it is not rarely a sign of the immature condition of the individual. The Chætodonts are most numerous in the neighbourhood of the coral-reefs of the Indo-Pacific, the species figured (_C. ephippium_) being as common in the East Indian Archipelago as in Polynesia, like many others of its congeners. CHELMO differs from _Chætodon_ only in having the snout produced into a more or less long tube. [Illustration: Fig. 168.--Chelmo marginalis, from the coast of Australia.] Only four species are known, locally distributed in the tropical seas. _Ch. rostratus_, the oldest species known, is said to have the instinct of throwing a drop of water from its bill so as to light upon any insect resting on a leaf, and thus make it fall, that it may instantly dart upon it. This statement is erroneous, and probably rests upon the mistaken notion that the long bill is especially adapted for this manœuvre, which, indeed, is practised by another fish of this family (_Toxotes_). The long slender bill of Chelmo (which is a true saltwater fish) rather enables it to draw from holes and crevices animals which otherwise could not be reached by it. HENIOCHUS.--One dorsal, with from eleven to thirteen spines, the fourth of which is more or less elongate and filiform. Snout rather short or of moderate length. Præoperculum without spine. Scales of moderate size. Four species are known from the tropical Indo-Pacific. _H. macrolepidotus_ is one of the most common fishes of that area; the species figured (_H. varius_) retains in a conspicuous manner horn-like protuberances on bones of the head, with which the young of all the species of this genus seem to be armed. [Illustration: Fig. 169.--Heniochus varius.] HOLACANTHUS.--Præoperculum with a strong spine at the angle. One dorsal, with from twelve to fifteen spines. Scales of moderate or small size.