FIG. 125.—Silver-jaw Minnow, _Ericymba buccata_ Cope. Defiance, Ohio. ] In America 225 species of _Cyprinidæ_ are known. One hundred of these are now usually held to form the single genus _Notropis_. This includes the smaller and weaker species, from two to seven inches in length, characterized by the loss, mostly through degeneration, of special peculiarities of mouth, fins, and teeth. These have no barbels and never more than four teeth in the main row. Few, if any, Asiatic species have so small a number, and in most of these the maxillary still retains its rudimentary barbel. But one American genus (_Orthodon_) has more than five teeth in the main row and none have more than two rows or more than two teeth in the lower row. By these and other peculiarities it would seem that the American species are at once less primitive and less complex than the Old World forms. There is some evidence that the group is derived from Asia through western America, the Pacific Coast forms being much nearer the Old World types than the forms inhabiting the Mississippi Valley. Not many _Cyprinidæ_ are found in Mexico, none in Cuba, South America, Australia, Africa, or the islands to the eastward of Borneo. Many species are very widely distributed, many others extremely local. In the genus _Notropis_, each river basin in the Southern States has its series of different and mostly highly colored species. The presence of _Notropis niveus_ in the Neuse, _Notropis pyrrhomelas_ in the Santee, _Notropis zonistius_ in the Chattahoochee, _Notropis callistius_, _trichroistius_, and _stigmaturus_ in the Alabama, _Notropis whipplei_ in the Mississippi, _Notropis galacturus_ in the Tennessee, and _Notropis cercostigma_ in the Sabine forms an instructive series in this regard. These fishes and the darters (_Etheostominæ_) are, among American fishes, the groups best suited for the study of local problems in distribution. [Illustration: FIG. 126.—Silverfin, _Notropis whipplei_ (Girard). White River, Indiana. Family _Cyprinidæ_. ] =Species of Dace and Shiner.=—Noteworthy species in other genera are the following: Largest and best known of the species of _Notropis_ is the familiar shiner or redfin, _Notropis cornutus_, found in almost every brook throughout the region east of the Missouri River. _Campostoma anomalum_, the stone-roller, has the very long intestines six times the length of its body, arranged in fifteen coils around the air-bladder. This species feeds on mud and spawns in little brooks, swarming in early spring throughout the Mississippi Valley, and is notable for its nuptial tubercles and the black and orange fins. [Illustration: FIG. 127.—Stone-roller, _Campostoma anomalum_ (Rafinesque). Family _Cyprinidæ_. Showing nuptial tubercles and intestines coiled about the air-bladder. ]