Description 



D. 13 (12); A. 18 (19); P. 17 (16-18); AO 7 (6-8) + 4 (3-5), total 11(10-12); gill rakers 8 + 1 -I- 

 18 (17-19), total 26-28; vertebrae 35. 



Distance from hind margin of orbit to upper opercular margin equal to or less than orbital 

 diameter; upper opercular margin neither striate nor serrate. Exposed margins of scales dis- 

 tinctly ctenoid. PLO about midway between pectoral origin and lateral line. 



Males have 2 (1-3) small supracaudal luminous glands, with rather heavily pigmented 

 margins, lying about over AOp-Prc interspace. Females have 1 (2) smaller infracaudal glands 

 with lightly pigmented margins, lying below the AOp-Prc interspace. The size at which these 

 fishes first develop luminous caudal glands is not known. 



Size: To about 65 mm. 



Least depth of capture: At surface at night. 



Distribution: Apparently similar to that of M. obtusirostrum. 

 Discussion 



The three species, Myctophum obtusirostrum, M. brachygnathum and M. pristilepis (Gil- 

 bert and Cramer, 1897) have usually been confused, particularly the latter two. Fraser- 

 Brunner (1949) placed M. pristilepis in the synonymy of M. brachygnathum , but Sarenas 

 (1954) regarded the two as distinct. Sarenas stated that in M. brachygnathum the distance 

 from hind margin of orbit to posterodorsal margin of operculum was greater than the length of 

 orbit, whereas these two characters were of nearly equal length in M. pristilepis; he also stated 

 that the scales of the latter were much more ctenoid than those of M. brachygnathum. In view 

 of the synonymy of these two species (see below), it seems possible that Sarenas worked with 

 misidentified material. 



Nafpaktitis (1973), after examining Bleeker's and Taning's type material and the 

 holotype of M. pristilepis, concluded that in M. obtusirostrum the distance from hind margin of 

 orbit to posterodorsal margin of operculum is greater than the length of orbit, but that these 

 two characters were of nearly equal length in M. brachygnathum. Nafpaktitis agreed with 

 Fraser-Brunner (1949) in placing M. pristilepis in the synonymy of M. brachygnathum. I have 

 examined several adult specimens of M. "pristilepis" from the central Pacific and have found 

 all body scales to be markedly ctenoid, whereas only a few weakly crenulate scales occur 

 anterolaterally near the pectoral fins in M. obtusirostrum. 



Myctophum selenoides 



Wisner, 1971 



Fig. 61 — Myctophum selenoides. holotype. male, 58.0 mm From Wisner 11971. p. 43, fig. 8.) 



66 



