KEY TO GENERA OF FAMILY MYCTOPHIDAE 



la. Primary photophores small, usually indistinguishable from minute secondary ones pres- 

 ent under each scale of head and body. Bases of dorsal and anal fins very long, about 



equal in length, their combined lengths contained about 1.75 times in SL Scopelopsis 



lb. Primary photophores larger than and readily distinguishable from any minute secondary 



ones 2 



2a. No more than 2 Pre. PO^ not elevated 3 



2b. More than 2 Pre. PO4 elevated or not 15 



3a. Base of adipose fin far behind vertical from end of anal base. VLO, SAO3, and Pol 

 far above lateral line near dorsal profile. Upper Pre well above lateral line and about 

 over the lower one. Prominent transparent dome covering pineal organ on top of 



head Notolychnus 



3b. Base of adipose fin over or slightly before or behind vertical from end of anal base. No 

 primary photophore above lateral line by more than about its diameter. Prc^ always 



behind vertical from Pre, 4 



4a. PLC far below origin of pectoral fin, about on level of base of lowest ray 5 



4b. PLC ranging from about level of pectoral origin to on or slightly above lateral line 7 



5a. Lateral line pores not visible. PLO and PVO, juxtaposed, nearly on same level and well 



below level of PVO^. AG series in continuous, nearly straight line Protomyctophum 



5b. Lateral line pores readily visible but the line incomplete in some genera 6 



6a. AG series undivided but often undulating near end of anal base, no distinct Pol. VO2 not, 

 or but slightly, elevated; VG series curved. PLO above PVO,, about level with PVO-, the 



three forming a right-angled triangle Electrona 



6b. AG series divided into AGa and AGp. One or more distinct Pol. VOo notably elevated, the 



series not curved, VG;, and VO^ about level with VG, Metelectrona 



7a. Mouth subterminal, a fleshy snout protruding notably. PLO slightly below or above 



pectoral origin. Lateral line absent or partly to entirely complete 8 



7b. Mouth terminal 11 



8a. Lateral line absent. Gill rakers reduced to tiny nubs tipped with 



spinules Centrobranchus 



8b. Lateral line present but incomplete in some genera 9 



9a. Least depth of caudal peduncle slightly greater than orbital diameter. Two to 4 VG 

 (rarely 5); 5 PO (rarely 4 to 8); 2 or 3 SAO. Palatine teeth fanglike. Lateral line incom- 

 plete, only a few anteriormost scales perforated Loweina 



9b. Least depth of caudal peduncle less than orbital diameter. Palatine teeth not 



fanglike 10 



10a. One Pre; 6 (5-9) PO; 6 VO. Lateral line poorly developed, only a few anterior scales 



perforated Tarletonbeania 



10b. Two Pre; 5 PO; 4 VG. Lateral line complete or nearly so, extending to at least near a 



vertical from adipose fin base Gonichthys 



11a. Prc2 at or near lateral line, far above level of Pre, 12 



lib. Pre2 clo.se Pre,, well below lateral line 13 



r2a. Two Pol. PVO, well below level of PVO^. VG series level. Both Dn and Vn present. Suo 



present, often indistinct. SAO series angulate Hygophum 



12b. One Pol. PVO, and PVO,. about on same level. VG- markedly elevated. Dn present, Vn 

 and Suo absent. SAO series angulate Benthosema 



10 



