=The Cyprinidæ.=—The chief family of the _Eventognathi_ and the largest of all the families of fishes is that of _Cyprinidæ_, comprising 200 genera and over 2000 species, found throughout the north temperate zone but not extending to the Arctic Circle on the north, nor much beyond the Tropic of Cancer on the south. In this family belong all the fishes known as carp, dace, chub, roach, bleak, minnow, bream, and shiner. The essential character of the family lies in the presence of one, two, or three rows of highly specialized teeth on the lower pharyngeals, the main row containing 4, 5, 6, or 7 teeth, the others 1 to 3. The teeth of the main row differ in form according to the food of the fish. They may be coarse and blunt, molar-like in those which feed on shells; they may be hooked at tip in those which eat smaller fishes; they may be serrated or not; they may have an excavated "grinding surface," which is most developed in the species which feed on mud and have long intestines. In the _Cyprinidæ_, or carp family, the barbels are small or wanting, the head is naked, the caudal fin forked, the mouth is toothless and without sucking lips, and the premaxillaries form its entire margin. With a few exceptions the _Cyprinidæ_ are small and feeble fishes. They form most of the food of the predatory river fishes, and their great abundance in competition with these is due to their fecundity and their insignificance. They spawn profusely and find everywhere an abundance of food. Often they check the increase of predatory fish by the destruction of their eggs. In many of the genera the breeding color of the males is very brilliant, rendering these little creatures for a time the most beautifully colored of fishes. In spring and early summer the fins, sides, and head in the males are often charged with pigment, the prevailing color of which is rosy, though often satin-white, orange, crimson, yellow, greenish, or jet black. Among American genera _Chrosomus_, _Notropis_, and _Rhinichthys_ are most highly colored. _Rhodeus_, _Rutilus_, and _Zacco_ in the Old World are also often very brilliant. [Illustration: FIG. 123.—Black-nosed Dace, _Rhinichthys dulcis_ Girard. Yellowstone River. ] In very many species, especially in America, the male in the breeding season is often more or less covered with small, grayish tubercles or pearly bodies, outgrowths of the epidermis. These are most numerous on the head and fall off after the breeding season. They are most developed in _Campostoma_. The _Cyprinidæ_ are little valued as food-fishes. The carp, largely domesticated in small ponds for food, is coarse and tasteless. Most of the others are flavorless and full of small bones. One species, _Opsariichthys uncirostris_, of Japan is an exception in this regard, being a fish of very delicate flavor. [Illustration: FIG. 124.—White Chub, _Notropis hudsonius_ (Clinton). Kilpatrick Lake, Minn. ] [Illustration: