252 



ZOOLOGY 



APPENDIX TO CHAPTER XVI 



KEY TO THE PRINCIPAL ORDERS OF FISHES 



i. Without skull, paired fins, or heart ; blood color- 



ACoo * 



a*. With skull, heart, and red blood [Craniota]. 

 61. Without lower jaw or paired fins 



b-2- With lower jaw and paired fins [Gnatho- 



stomij. 

 Ci. Intestine with spiral valve. 



d\. Without an operculum covering 

 the gill openings ; scales toothed 



dz- Operculate ; skin with enamelled 



scales. 



e\. Breathing by means of gills 

 only . . . 



e 2 . Breathing by both gills and 

 a lung .... 



c 2 . Intestine without spiral valve ; skele- 

 ton bony 



Acrania 



(Ex. Amphioxus) 



Cyclostomi 



(Lamprey eels) 



Selachii 



(Sharks and rays) 



Ganoidei 

 (Ganoid fishes) 



Dipnoi 



(Mud fishes) 



Teleostei 



(Bony Fishes) 



KEY TO THE SIX SUBORDERS OF TELEOSTEI 

 i. Gills comb-like. 



Ji. Intermaxillaries and maxillaries movable 



on each other. 

 Ci. Dorsal fin, anal fin, and ventral fin 



spinons anteriorly. 

 d\. Pharyngeal bones distinct . . Acanthopteri 



(Perches, darters, sunfishes, toadfishes, sculpins, silversides, 



sticklebacks) 



d-2. Pharyngeal bones united . . Pharyngognathi 

 c 2 . Dorsal, anal, and ventral fins without 

 spines. 



