FISHES OF LAKE SUPERIOR. 289 



The ground color is of a yellow, violaceous tint, much dark- 

 er above the lateral line than below. The back is spread with 

 blackish brown spots, sometimes disposed in two longitudinal rows, 

 sometimes in three, however without great regularity. On the 

 middle of the body extends a silvery ridge tapering slightly from the 

 head to the basis of. the caudal. It is not rare to see sometimes 

 blackish spots encroach upon this bright band. The fins are uni- 

 colored, and of a transparent whitish tint like that of the abdomen. 



We found this fish in great abundance at the Sault St. Mary, at 

 Michipicotin and at Fort William. 



PERCOIDS. 



Whenever we compare the fishes which occur in a given locality, 

 we are struck with peculiar associations entirely different from those 

 which we may find in other localities. Take the Bay of Massachu- 

 setts, for instance, where we have sharks, skates, &c., &c., combined 

 together in numeric proportions, and represented by species alto- 

 gether different from those which occur on the shores of the Middle 

 States or around Florida and in the Gulf of Mexico. Again, if we 

 compare freshwater fishes, as they occur in any extensive hydro- 

 graphic basin, for instance, those in the Canadian lakes, or in the Ohio 

 and Mississippi, or those of the lakes and rivers of Europe, with the 

 marine faunas, we find still more striking differences. Entire families 

 common in the sea under the same latitudes have no representative 

 in fresh water ; there are no sharks and no skates, no flounders, soles 

 or turbots, no mackerels, no herrings, as permanent inhabitants of 

 the freshwaters in the latitudes above mentioned ; so that a collec- 

 tion of species from the freshwater or from the sea, even if all 

 the species were to be new, could be recognized by an ichthyologist 

 as derived either from the ocean or from some inland water. 

 However different such associations of marine and freshwater 

 species may be, there is nevertheless scarcely any family, whether 

 generally marine or fluviatile, in which there is not some species 

 living in the other element. There are some families again, 

 in which the proportions between marine and fluviatile species are 



