Always more than 1 luminous organ at orbital margin; these organs are of varied size, 

 shape, and arrangement, and are connected by a varyingly wide band of darkly pigmented 

 tissue. Supracaudal and infracaudal luminous glands absent. A luminous scale of varied size 

 and shape at PLO is present in most species. Five VO, the first 3 in ascending series; 4 Pre. 



Key to species oi Diaphus in the eastern Pacific Ocean 

 la. So present (Fig. 84A). Ant absent. Inner series of teeth of posterior portion of upper jaw 

 broad-based, the tips sharply recurved 2 



Dn-- 



Dn 



elongated g^g,, 



V" Vn 



(never occurring 



together) 



B 



Dn- 



Vn- 



Fig. 84 — Sketches of orbital regions of adult and young-adult diaphid fishes of 

 the eastern Pacific Ocean, showing four combinations of luminous organs and 

 their approximate locations. 



lb. So absent. Ant absent or present (Fig. 84 B, C, D). Inner series of teeth of upper jaw 

 straight or slightly curved. If (rarely) slightly broad-based and recurved, it is to a much 

 lesser degree than in those species having an So 9 



2a. Pupil essentially round, no prominent (aphakic) space between lens and iris. Luminous 

 organs of head small, always well separated 3 



2b. Pupil elongated horizontally or vertically, a prominent (aphakic) space usually present 

 anteriorly between lens and pupil (Fig. 83). Luminous organs of head variable in size, not 

 necessarily well separated 4 



3a. Dn, Vn, and So small, about equal in size, connected by a thin strand of dark tissue. Body 

 photophores large, very closely spaced, the upper series low on body. SAO series in an 



98 



