GONOSTOMATIDAE 379 



B. Two series of photophores on each side of abdomen. 



I. Interorbital region rather wide; eyes normal; mouth large; teeth well developed; origin 

 of dorsal behind pelvics. 



a. No additional serial photophores on sides of body. 



* Origin of dorsal fin opposite to or behind that of anal. 



•j- Praemaxillary and maxillary with a continuous series of long acute teeth, set at 

 fairly regular intervals, with much smaller teeth in the interspaces between them ; 

 second suborbital more or less enlarged ; eye of moderate size ; anal with 22 to 

 31 rays. 3. Gonostoma 



■f-f Praemaxillary with few teeth ; maxillary with a series of small teeth, increasing 

 in size from before backwards, some of them at more or less irregular intervals 

 a little enlarged; second suborbital not enlarged; eye small; anal with 16 to 20 

 rays. 4. Cyclothone 



* Origin of dorsal fin in advance of that of anal. 



f Origin of dorsal fin a little in advance of that of anal, which commences below 

 its middle or posterior part. 



J Anal with 23 to 32 rays. 5. Yarrella 



XX Anal with 14 to 15 rays. 6. Vinciguerria 



■f-f Origin of dorsal fin well in advance of that of anal, which commences at some 



distance behind it. 7. Photichthys 



b. An additional series of photophores along the lateral line, and sometimes one or 

 more rows of luminous spots between these and the two abdominal series; no 

 adipose fin. 



* Body moderately elongate ; dorsal with i o to 16 rays, origin nearer to base of caudal 

 than end of snout ; anal with 26 to 39 rays. 8. Manducus 



** Body very elongate ; dorsal with 9 to 1 1 rays, origin a little nearer to end of snout 



than base of caudal ; anal with 55 to 63 rays. 9. Diplophos 



*** Body moderately elongate; dorsal with 10 rays, origin more than twice as near to 



end of snout as to base of caudal; anal with 56 to 71 rays. 10. Triplophos 



2. Interorbital region very narrow; eyes telescopic; mouth small, the lower jaw included; 

 teeth minute ; origin of dorsal in front of pelvics, which are nearer to base of caudal than 

 end of snout. ' 11. Ichthyococcus 



II. Photophores large and conspicuous; serial photophores on body more or less distinctly divided 

 into groups ; pseudobranchiae present. (Maurolicinae) 



A. Origin of dorsal fin in advance of that of anal. 



1. Series of photophores between pelvic and origin of anal separated from that above 

 anterior part of anal fin ; origin of dorsal nearer to base of caudal than end of snout ; 25 

 to 27 gill- rakers on lower part of anterior arch. 12. Mauroliciis 



2. Series of photophores between pelvic and origin of anal continuous with that above 

 anterior part of anal fin ; origin of dorsal nearer to end of snout than base of caudal ; 

 about 16 gill-rakers on lower part of anterior arch. 13. Argyripniis 



B. Origin of dorsal fin opposite to that of anal ; photophores above and behind the anal arranged 

 in four or five small groups, each group on a black background. 14. Valenciennellus 



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