Fig. 359. The File-fish (Balistes).
The Sclerodermes are distinguished by their conical or pyramidal muzzle, terminating in a little mouth armed with true teeth; their skin is generally stiff and covered with hard scales. The File-fish, Balistes and Coffers, are selected for notice. The File or Rudder-fish (Fig. 359) have the body compressed; the jaws are furnished with eight teeth, arranged in a single row on each jaw, and covered with true lips; the eyes are nearly level with the skin; the mouth is small, and the body enveloped in very hard scales, which are connected in groups and distributed into compartments more or less regular, and strongly connected by means of a thick skin. The animal is thus protected by a sort of cuirass and casque very difficult to penetrate.
With the exception of one species, the Balistes are inhabitants of Tropical seas. They are generally brilliantly coloured; they herd together in great numbers, and in their gambols produce curious combinations of brilliant colouring in the Equatorial seas. Their flesh is held in slight estimation, and at certain periods of the year is even said to be dangerous.
Fig. 360. The Coffer, or Ostracion.
The Coffers, or Ostracions (Fig. 360), are without scales, but covered with regular osseous compartments, which are so jointed the one to the other that the body is, as it were, enclosed in a kind of box or long coffer, which only reveals the external organs of locomotion—namely, the fins and a portion of tail. In some the body is triangular, in others quadrangular, with or without spines.
These singular fishes are found in the Indian Ocean and in the American seas. They are of moderate size, and are much prized in the United States as food.
II. Lophobranchii.
The Lophobranchii comprehend a few types, but are numerous in species. Here the gills are divided into small round tufts, and arranged in pairs along the branchial arches; a structure quite peculiar, of which we have no examples in any other fishes. These gills are enclosed under a large cover, or operculum, attached on all sides by a membrane, which leaves only a small hole for the escape of water which has served the purposes of respiration.