One family only belongs to this division.
Family—Kurtidæ.
Body compressed, oblong, deep in front, attenuated behind. Snout short. The spines of the short dorsal are few in number, if developed. Scales small or of moderate size. Villiform teeth in the jaws, on the vomer, and palatine bones.
This family consists of a small number of species only, which form two distinct genera, Pempheris and Kurtus. They are shore fishes of tropical seas. In both the air-bladder shows some peculiarity: in Pempheris it is divided into an anterior and posterior portion; in Kurtus it is lodged within the ribs, which are dilated, convex, forming rings. The number of vertebræ is respectively twenty-four and twenty-three.
Fourth Division—Acanthopterygii Polynemiformes.
Two rather short dorsal fins, somewhat remote from each other; free filaments at the humeral arch, below the pectoral fins; muciferous canals of the head well developed.
One family only belongs to this division.
Family—Polynemidæ.
Body oblong, rather compressed, covered with smooth or very feebly ciliated scales. Lateral line continuous. Snout projecting beyond the mouth, which is inferior, with lateral cleft. Eye lateral, large. Villiform teeth in the jaws and on the palate. Ventrals thoracic, with one spine and five rays.
The fishes of this natural family have been divided, on slight differences, into three genera—Polynemus, Pentanemus, and Galeoides. They are found in rather numerous species on the coasts between the tropics, and the majority enter brackish or even fresh water. Very characteristic are the free filaments which in this family are organs of touch; they are inserted on the humeral arch at some distance from the pectoral fin; but, nevertheless, can be regarded only as a detached portion of that fin; they can be moved quite independently of the fin; their number varies from three to fourteen, according to the species; in some they are exceedingly elongate, twice as long as the fish, in others they are not longer or even shorter than the pectoral. It is evident from the whole organisation of these fishes that they live on muddy bottom or in thick water, such as is found near the mouths of great rivers. Their eyes are large, but generally obscured by a filmy skin, so that those feelers must be of great use to them in finding their way and their food. The Polynemoids are very useful to man: their flesh is esteemed, and some of the species are provided with an air-bladder which yields a good sort of isinglass, and forms an article of trade in the East Indies. Some of these fishes attain to a length of four feet.