Page:Natural History, Fishes.djvu/70

56

A vast assemblage of species, amounting to about one-seventh of the whole Class, is seen by the preceding table to be comprised in this Family. They are, for the most part, marine fishes, though the typical genus, which gives a name to the Family, inhabits fresh waters. The form is generally long-oval; the body is covered with scales, the surface of which is more or less rough, and the free margins of which are notched like the teeth of a comb; the scales do not extend upon the fins; the gill-cover (operculum), and the gill-flap (preoperculum), are variously armed with spines, and cut into teeth at their margins. Both the upper and lower jaw are set with teeth, besides which, the bones of the palate and the vomer (or middle ridge of the roof of the mouth) are furnished with them, so that there are five rows of teeth above, and two below. In general, all the teeth are fine, and set in close array, so as to bear a remote resemblance, in appearance, to the pile of velvet. The branchiostegous rays, or the slender arched bones of the membrane that closes the great fissure of the gills beneath, vary in number from five to seven. The ventral fins are, in general, placed under the pectorals; the dorsal is either double or depressed in the middle.

So immense a Family cannot but comprise several varieties of form, which, while agreeing in the important characteristics that distinguish these Fishes from those of the other Families,