INTRODUCTION 



13 



SYSTEMATIC ZOOLOGY. 



On the ground of their relationship to one another, animals 

 have been classified into certain divisions and subdivisions, which 

 are designated as Classes, Orders, Suborders, Families, Genera, and 

 Species. 



A general classification of the principal existing Vertebrate 

 groups is given in the following table. 



A. Acrania. 



Amphioxus (Lancelet). 



B. Craniata. 



/ I. CYCLOSTOMATA (Suctorial Fishes). 



1. Petromyzontidse (Lamprey). 



2. Myxinoidse (Myxine, Bdellostoma). 



II. GNATHOSTOMATA (Animals provided with jaws). 



(a.) ANAMNIA (without amnion). 



1. PISCES (True Fishes). 



a. Elasmobranchii (Sharks and Rays). 



3. Holocephali (Chimsera and Callorhynchus). 



y. Ganoidei. 



1. Selachoidei (Cartilaginous Ganoids Aci- 



penser, Scaphirhynchus, Polyodon). 



2. Teleostoidei (Bony Ganoids Polypterus, 



Calamoichthys, Lepidosteus, Amia). 

 8. Teleostei. 



1. Physostomi (with open pneumatic duct 



between the air-bladder and pharynx, 

 e.g., Cyprinus, Salmo, Silurus, Mor- 

 myrus). 



2. Physoclisti (air-bladder, when present, 



with closed pneumatic duct, e.#.,Perca, 

 Gadus, Lophius, Labrus, Plectognathi, 

 Lophobranchii). 



2. DIPNOI. 



1. Monopneumones (Ceratodus). 



2. Dipneumones (Protopterus, Lepidosiren). 



3. AMPHIBIA. 



a. Urodela. 



1. Perennibranchiata (Proteus, Siren, 



Necturus). 



2. Caducibranchiata. 



Derotremata (Amphiuma, Menopoma). 



Myctodera (Salamandra, Triton, Am- 



blystoma). 



/3. Gymnophiona (Footless Csecilians). 

 y. Anura (Frogs and Toads). 



Ichthyopsida. 



