ARTIFICIAL KEY TO FAMILIES OF COMMON FISHES 65 



15. Jaws elongated, shaped like a duck's bill; large, irregular teeth; tail deeply 



forked esocidae (p. 185) 



Jaws not elongated; weak teeth; tail more or less rounded 16 



16. Upper jaw not protractile, formed by maxillary bone, .umbridae (p. 183) 

 Upper jaw protractile, formed by premaxillary bone 



CYERINODONTIDAE (p. 194) 



17. Gill-membranes united to isthmus (Diagram 2) 18 



Gill-membranes free from isthmus (Diagram 2) 19 



18. Dorsal fin with 10 or more rays; pharyngeal teeth numerous, in only one 



row CATOSTOMIDAE (p. 117) 



Dorsal fin with less than 10 rays (except introduced carp and goldfish) ; 

 pharyngeal teeth less than 10 on each side, in one or more rows 



CYPRINIDAE (p. 138) 



19. Lateral line present; tongue with sharp teeth hiodontidae (p. 88) 



Lateral line absent clupeidae (p. 90) 



20. Body scaleless, but covered with tiny spines or prickles; head large; eyes 



in top of head; pectoral fins very large cottidae (p. 250) 



Body with scales 21 



21. Vent anterior to pectoral fins aphredoderidae (p. 199) 



Vent posterior to pectoral fins : 22 



22. Single median barbel on chin gadidae (p. 258) 



No barbel on chin 23 



23. Anal spines, 2 or less 24 



Anal spines, 3 or more, first spine sometimes rudimentary 25 



24. Spinous and soft-rayed portion of dorsal fin completely divided into 2 sepa- 

 rate fins percidae (p. 204) 



Spinous and soft-rayed portion of dorsal fin confluent . sciaenidae (p. 247) 



25. Without longitudinal dark stripes on side of body, or with only one; dorsal 

 fins confluent (but deeply notched in largemouth bass) 



CENTRARCHIDAE (p. 226) 



With 5 or more usually distinct narrow, dark longitudinal strip>es on side of 

 body; dorsal fins either separate or deeply notched. . . .serranidae (p. 201) 



