BALIS'T ES, or a genus of osseous fishes of the order plectognathi (q.v.) of envier; the type of a family, the species of which are almost all inhabitants of tropical and subtropical seas, frequenting rocky coasts and coral-reefs. Their colors are generally brilliant. The body is remarkably compressed. The ossification of the skele ton, as in the other pleetognathi, is very incomplete, and the external covering of the body resembles that of the ganoid (q.v.) fishes, consisting, in some of the genera, of large rhomboidal scales, disposed in regular rows, and not overlapping; in others, of very small rough scales, with stiff bristles, as densely crowded as the pile of velvet. But the most interesting thing in connection with these fishes is the provision for fixing the first dorsal spine in an erect poositIon, 'or lowering it at the will of the animal. The spine is articulated "by ring and bolt to the broad interneural osseous plate." "When the spine
is raised, a depression of the back part of its base receives a corresponding projection from the contiguous base of the second ray, which fixes it like the hammer of a gun-lock at full cock, and it cannot be let down until the small spine has been depressed, as by pulling the trigger; it is then received into a groove on the supporting-plate, and offers no impediment to the progress of the fish through the water. This trigger-like fixing of the spine takes place also in the dead fish; and when a B. is removed from the Bottle for examination, it is generally necessary to release the spine by pressing on the small trig ger-ray." The spine is roughened with enamel grains, whence the name file-fish. The flesh of these fishes is generally regarded as unwholesome.