252 



ZOOLOGY 



APPENDIX TO CHAPTER XVI 



KEY TO THE PRINCIPAL ORDERS OF FISHES 



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

 less Acrania 



(Ex. Amphioxus) 



ao. With skull, heart, and red blood [Craniota]. 

 61. Without lower jaw or paired fins 



62- With lower jaw and paired fins [Gnatho- 



stomi]. 

 Ci. Intestine with spiral valve. 



d\. Without an operculum covering 

 the gill openings ; scales toothed 



$>. Operculate ; skin with enamelled 



scales. 



e\. Breathing by means of gills 

 only . . . . . 



eg. Breathing by both gills and 

 a lung .''- -, ... . . . 



eg. Intestine without spiral valve ; skele- 

 ton bony . . . . .'.'.' 



Cyclostomi 



(Lamprey eels) 



Selachii 



(Sharks and rays) 



Ganoidei 



(Ganoid fishes) 

 Dipnoi 



(Mud fishes) 



Teleostei 



(Bony Fishes) 



KEY "TO THE SIX SUBORDERS OF TELEOSTEI 



Gills comb-like. 



b\. Intermaxillaries and maxillaries movable 



on each other. 

 Ci. Dorsal fin, anal fin, and ventral fin 



spinous 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. 



