26a. Five VO, the second always, the third occasionally, elevated and displaced forward; 3 Pre 

 evenly spaced and usually separate from AOp. Upper photophores touching lateral line 

 either above or below it Triphoturus 



26b. Four VO, the second, but never the third, sometimes elevated and occasionally displaced 

 forward. Upper photophores sometimes touching, but never above lateral 

 line Lampanyctus 



27a. First AOa, and occasionally last, highly elevated 28 



27b. First AOa never last occasionally, elevated 29 



28a. Bases of dorsal fin notably longer than base of anal fin. Primary photophores large, 

 indistinct. Scales of luminous tissue in rows along bases of rays of dorsal and anal fins, 

 and elsewhere on body. No caudal luminous glands. SAO series forming straight, steeply 

 oblique line; 2 Pol in nearly horizontal line; 3 to 6 Pre Hintonia 



28b. Base of dorsal fin variably slightly longer or shorter than base of anal fin. Primary 

 photophores small but distinct. Scattered small scales of luminous tissue on body, often 

 arranged in short rows. No caudal luminous glands. SAO in straight, nearly vertical line. 

 One Pol; 4 to 9 Pre Gymnoscopelus 



29a. VO2 and VO3 elevat«d, the series curved. PV2 below origin of pectoral fin and on line 

 through PO, and PVO,; 2 Pol in steeply oblique line. Luminous scales on dorsal midline 

 before and behind, but not at base of, dorsal fin. Similar scales on ventral midline 

 between origins of pelvic and anal fins, along base of anal fin, at bases of ventral procur- 

 rent caudal rays, between PO, and PVO-, and near PLO. Infracaudal gland long, with 6-8 

 scales Ceratoscopelus 



29b. VO series level. PVO2 above origin of pectoral fin and about directly over PVO,; 2 or 3 

 Pol, at least 2 Pol in horizontal line 30 



30a. Base of dorsal fin much longer than base of anal fin. No photophores on cheek. No minute 

 secondary photophores on body; 2 or 3 Pol in a horizontal line; 3 Pre, the upper widely 

 distant from the first two. A few small scales of luminous tissue randomly scattered over 

 body, often in short rows above lateral line near head and below dorsal base and at bases 

 of procurrent caudal rays. Supraeaudal luminous gland large, infracaudal gland very 

 small Notoscopelus 



30b. Base of dorsal fin slightly shorter than base of anal fin. Three to five photophores on 

 cheek. Minute secondary photophore under each scale of body; 3 Pol, 2 near and parallel 

 with lateral line, a third directly below the anteriormost of the upper two; 4 Pre. Small 

 scales of luminous tissue scattered over body. Caudal luminous glands small and incon- 

 spicuous Lampichthys 



12 



