ZOOLOGY 



The whitefish (Coregonus 1 ), of which we possess many 

 species, is exclusively an inhabitant of fresh water. 2 Its 

 teeth are almost completely absent, or very small ; it feeds 

 almost exclusively upon small arthropods and mollusks. 

 It is of very great commercial importance, its fisheries 

 being valued tit nearly three million dollars a year. 



Leaving now the Salmonidse, we may briefly consider 

 some of the other more important families of bony fishes. 



FK;. 21-4. Morone americana, the white perch. The fish is searching for food 

 along the bottom of the aquarium, an instinct which it shows in nature also. 

 About one-third nat. size. Photo, of living animal by Dr. R. W. Shufeldt, 

 from " Bull. U. S. Fish Com.," 1899. 



The darters are spiny-rayed fishes of small size, from four 

 to seventeen centimetres long, brightly colored, and with 

 well-developed pectoral fins. They live in clear streams, 

 half concealed under stones, and are most abundant in the 

 Mississippi drainage basin. 



, the pupil of the eye ; ywvia, angle. 



2 Fig. 213. 



