34 VERTEBRATE ANIMALS OF THE UNITED STATES 



b2 Head wholly or partly scaly. 



Ci Lateral line wanting, or when present, imper- 

 fect and median in position, 

 di Lateral margin of upper jaw formed of the 

 maxillaries, the premaxillary being short ; 



pikes, pickerels 6. Haplomi (p. 90). 



d2 Upper jaw formed by the premaxilary; 



killifish, caveiish 7. Cyprinodontes (p. 93) 



Co Lateral line ventral in position (but one species 



in the United States); garfish 10. Synentognathi (p. 102) 



a2 Ventral fins thoracic or jugular (Fig. 3) in position, 

 (except in the Atherinidcr). 

 bi Fins without spines. 



Ci Head symmetrical; burbots 12. Anacanthini (p. 104). 



C2 Head asymmetrical; flatfish 13. Heterosomata (p. 105). 



b2 Fins with spines. 



Ci Anus jugular in position; pirate-perch 9. Xenarchi (p. loi). 



Co Anus normal in position. 



di Body uniformally covered with scales. 



ei Spinous dorsal fin with less than 16 spines. 

 fi Spinous dorsal with 6 to 15 spines; 



spiny-rayed fishes 14. Acanthopteri (p. 105). 



f2 Spinous dorsal with 2 to 8 spines; 



gobies 17. Gohioidea (p. 133). 



e2 Spinous dorsal fin with 16 or more 



spines; surffishes 15. Holconoti (p. 130). 



d2 Body without scales or irregularly scaled; 



sculpins 16. Calaphradi (p. 130). 



Order i. Isospondyli. — Herring; salmon; trout. Fishes with 

 unmodified anterior vertebras; lower pharyngeal arch simple, not 

 falciform; head not scaly; maxillary distinct from the premaxillaries 

 and forming part of the margin of the upper jaw; no barbels; air bladder, 

 if present, with a pneumatic duct; fins without spines; ventral fins 

 abdominal; scales usually cycloid, sometimes ctenoid, occasionally 

 wanting: 20 to 25 families, mostly marine; 2 suborders and 7 families in 

 fresh water. 



Key to These Suborders 



ai No adipose fin present i. Clupeoidei (p. 34). 



a2 Adipose fin present 2. Salmonoidei (p. 37), 



Suborder i. Clupeoidei. — Herring-like fishes; no adipose fin: 3 

 fresh water families. 



