FISHES 



6l 



ever natives of China, where they have been domesticated from time 

 immemorial. 



In the classification of these small fishes the lower pharyngeal teeth 

 (Fig. 30) are of great importance, and their number and form are 

 usually given in the descriptions. Thus "teeth 4-4" means that there 

 is a single row of 4 pharyngeal teeth on each side of the mouth; "teeth 



a b 



Fig. 30. — Lower pharyngeal teeth of the chub {Semolilus alromaculatus) : a, head of fish 

 with left opercle removed showing the left pharyngeal arch back of the gill-arches; h, the 

 two pharyngeal arches, the formula of the teeth being, 2, 4-5, 2 {from Fishes of Illinois). 



4-5" means there is a row of 4 teeth on one side and 5 on the other; 

 "teeth I, 4-5, 2" means there are 4 teeth in the main or hindermost 

 row and i tooth in the second or foremost row on one side, and on the 

 other side 5 and 2 teeth, respectively, in the two rows. In the herbiv- 

 erous species the teeth are nearly straight, and either without a hook 

 at the tip or with a slight hook. Near the base of the tooth is often a 

 masticatory surface in the form of a groove. 



Key to the Genera of United States Cyprinidae (not including the European Carp 



and the Goldfish) 



ai Digestive canal very long, being more than twice the length 

 of the body; peritoneum usually black. 



bi Digestive canal wound around air bladder 3. Campostoma. 



b2 Digestive canal not wound around air bladder. 



Ci Pseudobranchiie absent; on the Pacific slope 4. Orthodou. 



C2 Pseudobranchiae present. 



di Each jaw with a conspicuous horny plate; in the 



Columbia basin 5. Acrocheilus. 



dt Jaw without horny plate. 



ei Teeth in main row usually 5-5. 



fi Lateral Une complete; in California 6. Lavinia. 



£2 Lateral line incomplete; eastern and central 



States 7. Chrosomus. 



t2 Teeth in main row 4-4. 



fi First ray of dorsal fin not pecuUar. 



gi Teeth long and scarcely hooked 8. Hybognallius. 



g2 Teeth short and distinctly hooked 9. Dionda. 



