Salmonide 63 
and rarely enter streams except to spawn. In far northern 
regions they often descend to the sea; but in the latitude of the 
United States this is never possible for them, as they are unable 
to endure warm or impure water. They seldom take the hook, 
and rarely feed on other fishes. Numerous local varieties char- 
acterize the lakes of Scandinavia, Scotland, and Arctic Asia 
and America. Largest and most desirable of all these as a 
food-fish is the common whitefish of the Great Lakes (Coregonus 
clupetformis), with its allies or variants in the Mackenzie and 
Yukon. 
The species of Coregonus differ from each other in the form 
and size of the mouth, in the form of the body, and in the de- 
velopment of the gill-rakers. 
Coregonus oxyrhynchus—the Schnabel of Holland, Germany, 
and Scandinavia—has the mouth very small, the sharp snout 
projecting far beyond it. No species similar to this is found 
in America. 
The Rocky Mountain whitefish (Coregonus williamsont) has 
also a small mouth and projecting snout, but the latter is blunter 
Fic. 49.—Rocky Mountain Whitefish, Coregonus williamsoni Girard. 
and much shorter than in C. oxyrhynchus. This is a small 
species abounding everywhere in the clear lakes and streams of 
the Rocky Mountains and the Sierra Nevada, from Colorado to 
Vancouver Island. It is a handsome fish and excellent as food. 
Closely allied to Coregonus williamsoni is the pilot-fish, 
shad-waiter, roundfish, or Menomonee whitefish (Coregonus 
quadrilateralis). This species is found in the Great Lakes, the 
Adirondack region, the lakes of New Hampshire, and thence 
