48 VERTEBRATE ANIMALS OF THE UNITED STATES 



median crest armed with strong teeth; hyoid with a broad band of strong 

 teeth: 2 species, which are the largest of the trouts. 



C. namaycush (Walbaum). Mackinaw trout; lake trout (Fig. 23). 

 Length 900 mm.; head 4.5; depth 4; average weight 16 lbs.; extreme 

 weight 90 lbs.; color dark gray, often greenish on the sides, every- 

 where with rounded paler spots which are often tinged with reddish; 

 rays of dorsal fin 11; anal 11; scales 185 to 205; body elongate; head 

 very long; mouth large: northern North America from Maine to Van- 

 couver and northward to the Arctic and Alaska; common in the Great 

 Lakes, where after the sturgeon, it is the largest fish, and, after the 

 whitefish, the most important fish commercially. 



C. siscowet (Agassiz). Similar to C. namaycush, but with a deeper 

 body and an excessive development of fatty tissue beneath the skin; 

 color paler; scales 175: Lake Superior; abundant in deeper water; also 

 in Lakes Huron and Erie. 



4. Salvelinus Nilsson. Brook trout. Body moderately elongate, 

 spotted with red; scales very small and imbedded and hidden; vomer 

 elongate, with teeth on front end only, hinder portion depressed and 

 without teeth; hyoid with weak teeth or none: many species, which live 

 in cold, clear streams in the northern hemisphere, sometimes descending 

 into the sea; 4 species in the United States. 



Key to the Species of Salvelinus in the United States 



ai In the eastern and central States. 



bi Back marbled with dark olive and unspotted; sides spotted. . .S. foniinalis. 

 bo Back not marbled or spotted; sides spotted. 



Ci Rays of dorsal fin 13 ; anal 12 5. alpinus. 



C2 Rays of dorsal fin 10; anal 9 S. oquassa. 



C3 Rays of dorsal fin 9; anal 8 5. aureohis. 



a.2 On the Pacific slope S. parkei. 



5. foniinalis (Mitchill). Brook trout; speckled trout. Length 200 

 mm. or more; weight i lb. or more; extreme weight 8 lbs.; head and 

 depth 4.5; color of back and sides dark olive, marbled or barred on the 

 back and with numerous red spots on the sides, each spot margined with 

 brown; lower fins dusky, edged anteriorly with black and orange; rays 

 of dorsal fin 10; anal 9; scales 37-230-30: Maine to Montana and Sas- 

 katchewan; northward into Labrador; southward in the Appalachian 

 Mountains to Georgia; in none of the Great Lakes except Lake Superior; 

 introduced into other parts of the country; spawning occurs in the fall, 

 the eggs hatching the following spring. 



