Series Ostariophysi 



171 



of carp have been formed, the "leather-carp" (Lederkarpfen) 

 being scaleless, others, "mirror-carp" (Spiegelkarpf en) , having 

 rows of large scales only along the lateral line or the bases of 

 the fins. 



Closely allied to the carp is the goldfish (Carassius auratus}. 

 This is also a common Chinese fish introduced in domestication 

 into Europe and America. The golden-yellow color is found 

 only in domesticated specimens, and is retained by artificial 

 selection. The native goldfish is olivaceous in color, and where 

 the species have become naturalized (as in the Potomac River, 

 where it has escaped from fountains in Washington) it reverts 

 to its natural greenish hue. The same change occurs in the 

 rivers of Japan. The goldfish is valued solely for its bright 

 colors as an ornamental fish. It has no beauty of form nor 

 any interesting habits, and many of our native fishes (Percida, 

 Cyprinida) far excel it in attractiveness as aquarium fishes. 

 Unfortunately they are less hardy. Many varieties and mon- 

 strosities of the goldfish have been produced by domestication. 



The Catostomidae. The suckers, or Catostomidcz, are an off- 

 shoot from the Cyprinida, differing chiefly in the structure of the 

 mouth and of the lower pharyngeal bones. 

 The border of the mouth above is formed 

 mesially by the small premaxillaries and 

 laterally by the maxillaries. The teeth of 

 the lower pharyngeals are small and very 

 numerous, arranged in one series like the 

 teeth of a comb. The lips are usually thick 

 and fleshy, and the dorsal fin is more or less 

 elongate (its rays eleven to fifty in number), 

 characters which distinguish the suckers from 

 the American Cyprinid generally, but not 

 from those of the Old World. 



About sixty species of suckers are known, 

 all of them found in the rivers of North 

 America except two, which have been re- 

 corded on rather uncertain authority from 

 Siberia and China. Only two or three of 

 the species extend their range south of the 

 Tropic of Cancer into Mexico or Central America, and none 



FIG. 133. Lower pha- 

 ryngeal of Placopha- 

 rynx duquesmi (Le 

 Sueur). 



