50 FISHES OF ILLINOIS 



border of eye; lower jaw slightty projecting; gill-rakers 26 +49=75. 

 Dorsal rays 18; anal 18. 



Ohio River at Louisville, whence the types were obtained by 

 Dr. Evermann in 1897 and 1898. 



Family SALMONID^E 

 (the salmon family) 



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

 lateral line present ; skeleton bony ; anterior vertebrge not modified ; ven- 

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

 forked; mesocoracoid present; gill-membranes free from isthmus; branchi- 

 ostegals 10 to 20; pseudobranchiae present; gill-rakers various; mouth 

 terminal; maxillary forming lateral margin of upper jaw; a supplemental 

 maxillar}^ present; premaxillaries not protractile; teeth various, some- 

 times wanting; stomach siphonal; pyloric Cceca numerous; air-bladder 

 large, with open duct; ova large, falling into abdominal cavity before ex- 

 clusion. 



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 choic- 

 est 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 Gexera of SALMONID^E 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 

 moderate, 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, with the cutting edge nearlv horizontal and 

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

 35, long and slender Argyrosomus. 



