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. 



B. Craniata. 



I. CYCLOSTOMATA (Suctorial Fishes). 



1. Petrcmyzontidae. 



2. Myxinoidse. 



II. GXATHOSTOMATA (Animals provided with jaws). 

 (a.) Ax AM NI A (without amnion). 



1. PISCES (True Fishes). 



a. Elasmobranchii (Sharks and Rays). 



/3. Holocephali (Chimaera and Callorhynchus). 



y. Ganoidei. 



1. Selachoidei (Cartilaginous Ganoids Aci- 



penser, Polyodon, &c.). 



2. Teleostoidei (Bony Ganoids Polypterus, 



Lepidosteup, Amia, &c.). 

 8. Teleostei. 



1. Physostomi (with open pneumatic duct between 



the air-bladder and pharynx, e.g. Cyprinus, 

 Salmo, Silurus, Mormyrus). 



2. Physoclisti (air-bladder, when present, with 



closed pneumatic duct, e.g. Perca, Gadus, 

 Ichthyopsida. Lophius). 



2. DIPNOI. 



1. Monopneumones (Ceratodus). 



2. Dipneuuiones (Protopterus). 



3. AMPHIBIA. 



a. Urodela. 



1. Perennibranchiata (Proteus, Siren, Monobran- 



chus). 



2. Caclucibranchiata. 



Derotremata (Amphiuma, Menopoma). 



Myctodera (Salamandra, Triton, Ambly- 



stoma). 



/3. Anura (Frogs and Toads). 

 y. Gymnophiona (Footless Caecilians). 



