116 University of Washington Publications in Biology [Vol.2. 



22b. Body covered with scales. 



24a. Origin of dorsal fin little if any behind middle of 

 body. 

 25a. Sides of body without photophores or luminous 

 spots; head without scales. 



26a. Dorsal and anal each with 1 or 2 spines. 



Trout Perches 40. Percopsidae, p. 156 



26b. Dorsal and anal of soft rays only. 



27a. Pelvic fin with a scaly appendage above its 

 base ; stomach with more than 1 1 pyloric caeca ; 

 dorsal fin base, shorter than length of head. 



28a. Maxillary extending to posterior edge of, or 

 behind eye in adult ; dentition strong ; mouth 

 deeply cleft; scales in more than 115 oblique 

 rows on side of body. 



Salmon and Trout 



20. Salmonidae, p. 133 



28b. Maxillary not extending behind eye, usually 

 ending before or just at anterior edge of 

 eye ; dentition weak ; scales in fewer than 

 105 oblique rows on side of body. 



29a. Dorsal fin of fewer than 17 fin rays. 



Whitefishes 21. Coregonidae, p. 139 



29b. Dorsal fin of 20 to 24 fin rays. 



Grayling 22. Thymallidae, p. 140 



27b. Pelvic fin without a scaly appendage above its 

 base; stomach with 11 or fewer pyloric caeca. 



30a. Mouth large, the maxillary reaching un- 

 der eye; both jaws with teeth; tongue 

 with teeth on upper surface. 

 Smelts 23. Osmeridae, p. 140 



30b. Mouth small, maxillary not extending un- 

 der eye ; premaxillary toothless ; tongue 

 toothless except probably fine teeth on 

 sides. 



31a. Branchiostegals about 6. Fig. 12. 



24. Argentinidae, p. 142 



31b. Branchiostegals 3 or 4. Fig. 12. 



25. Microstomidae, p. 142 



25b. Sides of body with photophores; head without 

 scales. Fig. 9. 



32a. Pseudobranchiae present. 



Lantern Fishes . . .33. Myctophidae, p. 151 



32b. Pseudobranchiae absent ; teeth canine-like. 



33a. Opercles incomplete, interopercle rudimen- 

 tary; fig. 10; origin of dorsal in front of 

 base of pelvic fin; gill rakers absent. 



Viper Fishes 



26. Chauliodontidae, p. 142 



