374 LAKE SUPERIOR. 



drawing the conclusions which follow directly from these facts, I 

 should introduce a similar list of the fishes living in similar latitudes, 

 or under similar circumstances, in other parts of the world ; and more 

 particularly of the species of Northern Europe. But such a list, to 

 be of any use, should be throughout based upon a critical compara- 

 tive investigation of all the species of that continent, which would 

 lead to too great a digression. The comparison of the freshwater 

 fishes of Europe, which correspond to those of North America, has 

 been carried so far, that I feel justified in assuming, what is really 

 the fact, that all the species of North America, without a single ex- 

 ception, differ from those of Europe, if we limit ourselves strictly to 

 fishes which are exclusively inhabitants of freshwater. 



I am well aware that the salmon which runs up the rivers of 

 Northern and Central Europe, also occurs on the eastern shores of the 

 northern part of North America, and runs up the rivers emptying into 

 the Atlantic. But this fish is one of the marine arctic fishes, which 

 migrates with many others annually further south, and which migra- 

 tory species is common to both continents. Those species, however, 

 which never leave the freshwaters, are, without exception, different 

 on the two continents. Again, on each of the continents, they differ 

 in various latitudes ; some, however, taking a wider range than 

 others in their natural geographical distribution. 



The freshwater fishes of North America, which form a part of its 

 temperate fauna, extend over very considerable ground, for there is 

 no reason to subdivide into distinct faunce the extensive tracts of land 

 between the arctics and the Middle States of the Union. We notice 

 over these, considerable uniformity in the character of the freshwater 

 fishes. Nevertheless, a minute investigation of all their species has 

 shown that Lake Superior proper, and the freshwaters north of it, 

 constitute in many respects a special zoological district, sufficiently 

 different from that of the lower lakes and the northern United States, 

 to form a natural division in the great fauna of the freshwater fishes 

 of the temperate zone of this continent. 



We have shown that there are types, occurring in all the lower 

 lakes, which never appear in Lake Superior and northwards, and 

 that most of the species found in Lake Superior are peculiar to it ; 

 the Sahnonidse only taking a wider range, and some of them covering 



