50 FISHES OF ILLINOIS 



Ohio River at Louisville, whence the types were obtained 

 by Dr. Evermann in 1897 and 1898. 



Family SALMONID^zE 



the salmon family 



Body oblong or elongate, covered with cycloid scales; head naked; 

 lateral line present; skeleton bony; anterior vertebrae not modified; ventral 

 fins abdominal; dorsal fin about median; adipose fin present; caudal forked; 

 mesocoracoid present; gill-membranes free from isthmus; branchiostegals 

 10 to 20; pseudobranchige present; gill-rakers various; mouth terminal; 

 maxillary forming lateral margin of upper jaw; a supplemental maxillary 

 present; premaxillaries not protractile; teeth various, sometimes wanting; 

 stomach siphonal; pyloric caeca numerous; air-bladder large, with open 

 duct; ova large, falling into abdominal cavitj^ before exclusion. 



Fresh waters and seas of northern regions of Europe, Asia, 

 and America; many species anadromous; genera, 10; species 

 about 70; 5 genera found in fresh waters of the United States 

 and Canada. 



Most of the species are of moderate or large size, and are 

 prized for their food qualities. Among them also are numbered 

 the choicest of all fresh-water game fishes. They are the best 

 adapted of all fishes to the purposes of artificial culture, which 

 in recent years has aided materially in keeping up their fisheries. 

 The fact that the eggs can be transported long distances in ice 

 without injury has made possible the introduction of American 

 and British forms into some of the temperate regions of the 

 southern hemisphere. 



Key to the Genera of SALMONIDi^ found in Lake Michigan and 



Adjacent Waters 



a. Mouth not deeply cleft, the mandible articulating with the quadrate bone under 



or before the eye; dentition more or less feeble or incomplete; scales moder- 

 ate, 60 to 95 in lateral line. 



b. Mouth rather small; lower jaw usually included and overhung by the more 



or less projecting snout; premaxillaries broad, with the cutting edge nearly 

 vertical or directed backward; gill-rakers on long limb of first arch usually 



fewer than 30 and rather short Coregonus. 



bb. Mouth larger, the lower jaw usually more or less projecting beyond upper; 

 premaxillaries rather narrow, witli the cutting edge nearly horizontal and 

 directed forward; gill-rakers on long limb of first arch usually more than 

 35, long and slender Argyrosomus. 



