CLASS I. FISHES 



Aquatic, cold-blooded vertebrates which have an integumentary 

 covering of dermal scales or plates, and which breathe by means of 

 pharyngeal gills. Median and paired fins are in most cases present, 

 the latter being homologous to the limbs of the higher vertebrates. 

 The heart has but one ventricle and one auricle, and contains only 

 venous blood. The head is joined with the trunk without articulation, 

 and there is no neck. No external ear-opening is present. With 

 a few exceptions all fishes lay eggs, which develop without an amnion. 



Number of Species and Distribution. — About 12,000 species of 

 fishes have been described, of which about 600, grouped in about 34 

 families and 2 subclasses, live in the fresh waters of the United States. 

 Of these families the largest are the Cyprinidce with 230 species and the 

 PercidcB with 72 species; the CyprinodontidcE with 52 species and the 

 Catostomidce with 51 species are the next in rank; and these four fami- 

 lies include two-thirds of all the species of fresh water fishes in the 

 country. 



The fresh waters of the United States are very rich in species of 

 fishes, as will be seen by a comparison with those of Europe, which, 

 although having a land area of about the same extent and with a very 

 varied surface, contains only about 125 species. It is the very large 

 hydrographical basins of our country joined with its varied character 

 and the relatively high temperature of the middle and southern portions 

 of it which have brought about the multipHcation of species of fishes 

 within its borders. The Mississippi basin contains about 200 species 

 and that of the Great Lakes about 150 species. 



History. — Fishes, conspicuous and abundant animals as they 

 are and important in the dietary of all peoples, have attracted the 

 interest of naturalists from time immemorial. The modern scientific 

 study of them is based upon the classifications of Peter Artedi and 

 Linnaeus, who wrote in the i8th century, and Cuvier, who wrote in 

 the early part of the 19th. In recent times the most important single 

 work is Giinther's ^'Catalogue 0} the Fishes of the British Museum,'^ 

 published in 1859-70. This- work and Boulenger's continuation of 

 it published in 1 898-1 900 are fundamental for the modern systematic 

 study of fishes. The fishes of America have attracted many brilliant 

 students, the most eminent of the earlier ones being Louis Agassiz, 

 who first placed the study of American fishes on a sound scientific 



