Fishes of the Western North Atlantic lOi 



15 b. Upper jaw not extending rearward ap- 

 preciably beyond eye; dorsal profile of 

 head straight to weakly convex; body 

 deepest about at dorsal fin. 

 1 6 a. Origin of rayed dorsal nearer to 

 gill opening than to adipose dorsal 

 by a distance of slightly less to 

 considerably more than head 

 length. 



17a. Pupil round; entire posterior 

 edge of opercular flap formed 

 by subopercular bone. 



Aulopidae, Part 5. 

 17b. Pupil keyhole-shaped; pos- 

 terior edge of opercular flap 

 formed by opercle above, 

 and by subopercle below. 

 Chlorophthalmidae, Part 5. 

 1 6 b. Origin of rayed dorsal almost or 

 quite as near to adipose dorsal as 

 to gill opening, and much nearer 

 to adipose dorsal in some. 



Osmeridae, Part 3, p. ^c,-},. 

 lb. No rayed dorsal fin; only an adipose dorsal fin. Anotopteridae, Part 5. 



Key C. Photophores present on head, or on body, or on both; or with eyes 



ON top of head. 

 I a. Eyes without lenses, covered by frontal bones, and consisting of large and flat 

 plates that occupy more than half of dorsal surface of head. 



Ipnopidae in part. Part 5.^^ 

 I b. Eyes with lenses, not covered by the frontal bones and, if dorsally directed, oc- 

 cupying less than half of dorsal surface of head. 



2 a. One or more barbels on chin, usually long and fleshy but sometimes very 

 small. 



3 a. Dorsal fin mostly or wholly anterior to anal, its origin near midlength 

 of trunk. 



4 a. Dorsal base extending behind pelvics, its origin behind or only 

 slightly before pelvic base; first dorsal ray not prolonged. 



Astronesthidae, Part 4. 



52. For those without these organs, see Key A, 7 a. 



