CHAPTER IX 



INTRODUCTION TO THE VERTEBRATA : DESCRIPTION OF THE 

 DOGFISH AS ILLUSTRATING THE GENERAL STRUCTURE OF 

 A VERTEBRATE 



SCHEME OF CLASSIFICATION 



CEPHALOCHORDA Amphioxus. 



CYCLOSTOMATA -Lampreys (Petromyzon) ; Hagfish (Myxine) and Borers 



(Bdellostoma). 



ELASMOBRANCHII Sharks and Dogfish ; Rays and Skates. 

 TELEOSTOMI 



I. Crossopterygii Polypterus, Calamichthys. 

 II. Actinopterygii 



A. Ganoidei Sturgeons (Acipenser), Garpike (Lepidosteus), 



Bowfin (Amid). 



B. Teleostei Herring, Salmon ; Carp, Catfish, Eel, Pike, Cod, 



Perch, Flounder, Sole, and the great majority of ordinary 

 fishes. 



DIPNOI Lungfish (Lepidosiren, Protopterus, Ceratodus). 



AMPHIBIA Urodela (Newts, Salamanders), Anura (Frogs, Toads), Apoda 

 or Gymnophiona. 



REPTILIA Rhynchocephalia (Sphenodon), Lizards (Lacertilia), Snakes 

 (Ophidia), Tortoises and Turtles (Chelonia), Alligators (Crocodilia), 

 and many interesting extinct groups known from the fossil remains 

 of their skeletons. 



AVES Birds. 



MAMMALIA Mammals, including all Vertebrates with hair and milk- 

 glands from the Duckbill and Opossums and their allies ,up to and 

 including Man. 



A GLANCE through the list given above will show that the phylum Verte- 

 brata includes a large proportion of the most familiar and best-known 



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