INTRODUCTION 



The waters of our oceans teem with plant and animal 

 life comprising numerous species, many as yet undiscov- 

 ered. The animals may be divided into two main groups: 

 invertebrates, that is, animals without backbones, such 

 as the jellyfish, the starfish, clams and oysters, crabs and 

 lobsters; and vertebrates, that is, animals with backbones, 

 including lampreys, sharks, rays, skates, fishes, whales, and 

 porpoises. 



In popular language the term "fish" includes the lam- 

 preys, the sharks, the rays and skates, the bony fishes, and 

 frequently even the whales and porpoises. With increased 

 dissemination of scientific information, more people have 

 come to recognize that the whales and porpoises are not 

 fishes but belong to the class Mammalia which also in- 

 cludes man. However, few realize that the lampreys, 

 sharks, rays, and skates are no more true fishes than are 

 whales or porpoises. The lampreys are members of the 

 class Cyclostomata, the sharks, rays, and skates of the 

 class Chondricthyes, and the bony fishes, or true fishes, 

 of the class Osteichthyes. 



Without going into the technical reasons for assigning 

 these various animals to different classes, it can be stated 

 that the lampreys and the sharks, rays, and skates are as 

 different from each other and from the bony or true fishes 

 as are the whales and porpoises^. However, traditionally 

 the ichthyologist has accepted responsibility for the study 

 of the lampreys, sharks, rays, and skates along with the 

 true fishes, and they are accordingly included in this 

 publication. 



As far as the marine fishes and fish-like vertebrates are 

 concerned, the American Atlantic coast may be divided 

 into three zones: a cold-water zone north of Cape Cod, 



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