282 



FISHES. 



Semotilus, the red appears chiefly as pigment in the 

 membranes of some or all of the fins, the sides of the 

 body being usually more or less flushed; in Bhinichthys 

 and Gila, the black of a portion of the lateral band 

 usually changes to red; in Ghrosomus, and Phoxinus, 

 the pigment lies mostly in the skin of the belly, and 

 in Minnilus it is chiefly about the head and the bases 

 of the fins. In Pimephales and Hyhorhynchus, black 

 pigment is deposited in the skin of the head, and in the 

 species of the sub-genus Photogenis, satin - white pig- 

 ment occurs in the fins. So far as is known to me, 

 species of Hemitremia, Hyhognathus, CoUscus, Phena- 

 cobvus, Exoglossum, Ericymba and some species of 

 other genera show no special variations in the breeding 

 season. 



Note. — ^Young Oyprinidx usually are more slender than adults 

 of the same species, and the eye is always much larger ; they also 

 frequently show a black lateral stripe and caudal spot which the 

 adults may not possess. Spots on the flns are generally charac- 

 teristic. 



The student will find it necessary from the first to examine very 

 carefully the teeth of these fishes, as the genera, as now accepted, 

 are largely based on dental characters. The phaiyngealv hones in 

 the smaller species can be removed by inserting a pin (or better, a 

 small hook) through the gill-opening, under the shoulder-girdle. 

 The teeth should be carefully cleaned with a tooth-brush, or better, 

 a jet of water, and when dry may be examined hy any sort of hand 

 magnifying-glass. In most cases a principal row of four or five 

 larger teeth will be found, in front of which is a set of one or two 

 smaller ones. The two sides are usually but not always sym- 

 metrical. Thus, " teeth 2, 4 — 5, 1," indicate two rows of teeth on 

 each side, on the one side, four in the principal row and two in 

 the lesser, on the other side five in the main row and one in the 

 other. "Teeth 4 — 4" indicates a single row of four on each 

 pharjmgeal bone, and so on. 



In most of our genera, these teeth — or the principal ones, are 

 " raptatorial," that is, hooked inward at the tips. A '• grinding " or 



