THE AQUATIC VERTEBRATES 



1031 



less and fanged, naked and scaled, barbeled and not, nocturnal 

 and diurnal, bottom sitters and top skimmers, riffle inhabitants and 

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

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

 possible fish environment. The same gamut of size, shape, and 



FIG. 1536. Long-Eared Sunfish, Lepomis megalolis (Rafinesque). Actual size, 90 mm. long. 



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

 America though the twc continents have no 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 families 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. 



