In addition to these troublesome groups, there are a few specimens before me, in poor 

 condition, that bear such abnormalities as 5 VO, or the SAO, well behind a vertical from VO4. 

 These specimens, not discussed further, cannot now be properly assigned, because other useful 

 characters are too often eroded away. Also, many specimens, obviously Lampanyctids, are 

 unidentifiable because of severe damage to head and body, or complete denudation — conditions 

 common in the more fragile species. 



Key to species of Lampanyctus 



la. Pectoral fin short, weak, narrow-based, or entirely absent. If present, width of the base 

 equal to or less than shortest distance between lower orbital margin and toothed margin 

 of upper jaw. No prominent photophore on cheek, but a small Bu may be present pos- 

 teroventrally just above margin of upper jaw. No luminous gland at base of adipose fin; 

 no minute secondary photophores under scales of body and head 2 



lb. Pectoral fin long, broad-based; width of base greater than shortest distance between 

 lower orbital margin and toothed margin of upper jaw. Some species bear 1 or more 

 prominent photophores on cheek, a luminous gland at base of adipose fin, and minute 

 secondary photophores under scales of body and head 7 



2a. VLO well below lateral line 3 



2b. VLO ator near lateral line 6 



3a. SAO, over or slightly before VO4. SAO2 well behind, SAO3 far behind, origin of anal base. 

 Bu present L. idostigma 



3b. SAO, about over VOs. SAO-, over or slightly before origin of anal base. Bu present 4 



4a. Photophores notably small. SAOj and SAO3 both before anal origin. VLO well above a 

 line from SAO i.^. Bu present L. regalis 



4b. Photophores not notably small 5 



5a. SAOj about over, SAOs slightly behind, anal origin. VLO on a line from SAO, .2. Bu 



present. Infracaudal gland with 6 (5-7) luminous scales filling three-fourths or less of 

 infracaudal space L. ritteri 



5b. SAOi; well before, SAO.) well behind, anal origin. VLO slighly above line from SAO,.... 

 VO2 slightly but distinctly elevated. Bu present; 8-9 (7-10) luminous scales in in- 

 fracaudal gland filling, or nearly so, infracaudal space L. fernae 



6a. Infracaudal gland with 7 to 9 luminous scales. Pectoral fin absent or reduced to a few 

 filamentous rays. SAO,, above third or fourth anal ray. Upper Pol on or slightly behind 

 vertical from base of last anal ray L. achirus (A complex) 



6b. Infracaudal gland with 3 to 5 luminous scales. Pectoral fin usually present but small and 

 fragile. SAO,, over origin of anal base. Upper Pol before vertical from base of last anal 

 ray L. niger 



7a. No photophores on cheek; no luminous scale at base of adipose fin; no minute secondary 

 photophores on body 8 



7b. One or more photophores on cheek; 1 or more luminous scales at base of adipose fin 

 (absent in one species); minute secondary photophores present and more or less prom- 

 inent 17 



8a. First 3 Pre in a slightly curved, nearly horizontal line; Prc^ usually widely separate from 

 the rest 9 



8b. First 3 Pre not on a nearly horizontal line, last 3 about equally spaced on an oblique, 

 usually straight line; Prc4 not widely separate from the rest 12 



9a. Nine to 11 procurrent caudal rays. VO2 elevated but not displaced forward, VO series 

 curved and about equally spaced. AOa series curved. Seven to 8 luminous scales in 

 infracaudal gland L. acanthurus 



9b. No more than 8 ventral procurrent caudal rays 10 



168 



