1936] Schultz: Keys to Fishes 119 



Fig. 8. The head of a catfish showing the pectoral spine and the location of the bar- 

 bels; Ba — barbels; Pec Sp — pectoral spine. 



Fig. 9. A lantern fish, Myctophidae, showing the arrangement and names applied to 

 the photophores. Aao — anterior anal organs; Pao — posterior anal organs; Pco — precaudal 

 organs; PI — posterior lateral organs; Sbp — suprapectoral organ; Spa — supra-anal organs; 

 Spcs — supracaudal luminous scales; Spp — suprapectoral organ; Spv — supraventral organ; 

 Th — thoracic organs; Veo — ventral organs. Modified after Parr. 



Fig. 10. A sketch showing the arrangement and names of the opercular bones in 

 Sebastodes caurimis. Ope — operculum; I Ope — interoperculum; P Ope — preoperculum; 

 S Ope — suboperculum. 



Fig. 11. The Pacific Saury, Cololabis saira, showing the finlets behind the dorsal and 

 anal fins. Drawn by Arthur D. Welander. 



Fig. 12. The ventral side of the head of Myoxocephalus polyacanthocephalus to show 

 the free fold of the gill membrane across the isthmus. Br. — branchiostegal ray; Br Mem — 

 branchiostegal or gill membranes broadly joined to each other; Fo 1st — gill membranes 

 forming a free fold across the isthmus by being unattached along their margins; Pec — 

 pectoral fin; Ve — ventral or pelvic fin. Modified after Jordan and Evermann. 



Fig. 13. The ventral side of the head region of Catostomns macrocheilus, the Colum- 

 bia River coarse-scaled sucker, showing the corners of the mouth without the notches in 

 the lips. Br 1st — branchiostegal or gill membranes broadly joined to the isthmus; Inc — 

 incision in the lower lip; Mo — mouth. Drawn by Arthur D. Welander. 



'^>x--\-J3kUt 



Fig. 14. A diagram of a hypothetical flatfish, Plenronectidae, to show the various 

 modifications of the lateral line and the asymmetry of the head. Ar Lat — a distinct arch 

 in the lateral line; Db Lat — dorsal branch of the lateral line; N Ar Lat — no distinct arch 

 in the lateral line. 



41a. Mouth terminal ; not excessively large ; 

 maxillary not nearly reaching to gill open- 

 ings. 



Herrings and Shad 



17. Clupeidae, p. 133 



41b. Mouth inferior, below a tapering snout ; 

 mouth very large, the maxillary reaching 

 nearly or quite to gill openings. 

 Anchovies 18. Engraulidae, p. 133 



40b. Lateral line present; dorsal fin in posterior 

 3rd of body. 

 19. Alepocephalidae, p. 133 



39b. Branchiostegals 3 ; gill membranes united to 

 the isthmus; fig 12; gill rakers not long and 

 slender; lateral line usually present. 



