THE AQUATIC VERTEBRATES 



103 1 



less and fanged, naked and scaled, barbeled and not, noctur. al 

 and diurnal, butlom sitters and top skimmers, rittlc inhabitants and 

 pool dwellers, raud-puddlers and mountaineers, round-bellied and 

 serrate-edged. They are adapted, in short, to all conditions of 

 possible fish environment. I'he same gamut of size, shape, and 



Fig. 1536. Long-Eared Sunfish, Lcpomis mei^alotis (Rafine^Que). Actual size, go mm. long. 



habit is found in the fresh waters of South America and North 

 America though the two continents ha^•e nc fishes in common. 

 The members of different families have thus independently become 

 convergently and divergently adapted. 



Fresh-water fishes do not form a group by themselves. Various 



Fig. 1537. Little Pickerel, Lucius vermiculalus (Le Sueur). Actual size, 119 mm. long. 



marine famihes have contributed to the fauna. But the larger 

 per cent of the fresh-water fishes belong to the single superorder 

 Ostariophysi. Of the 600 fresh-water species of North America, 

 307, or over half, belong to this group. 



