526 PROCEEDINGS OF THE NATIONAL MUSEUM vol.86 



The dorsal is short and high, its longest ray (the fourth) reaches 

 past the end of the fin base to the origin of the adipose. The adipose 

 lies over the posterior fourth of the anal fin ; its free portion is slightly 

 longer than its base. The pectorals are inserted moderately high on 

 the body and are good sized. Their rays reach beyond the anterior 

 SAO and nearly to the insertion of the anus. The pelvics are inserted 

 on the ventral contour of the body a Uttle nearer the insertion of 

 the pectorals than the origin of the anal. Their longest rays extend 

 past the anus to the third or fourth ray of the anal fin. The anal is 

 long and moderately liigh, its longest ray (the third) when depressed 

 reaches two-thirds of the length of the base of the fin; it originates 

 under the posterior tliird of the dorsal. 



There are the usual three photophores on the under jaw, the small 

 one at the end of the premaxillary, and the larger one directly above 

 on the angle of the preopercle. The PLO is well below the base of 

 the pectoral fin, on a level with the most anterior and ventral of the 

 two PVO and is nearly hidden by the edge of the subopercle. The 

 ventral PVO lies a third of the way along a straight line from the 

 dorsal PVO to the most anterior of the PO series. There are 5 PO, 

 all of which are on the same level; but the last three are closer together 

 than the first two. The VLO is about midway between, and forms a 

 straight line with the dorsal PVO and the most anterior SAO. There 

 are 4 VO all on the same level. The middle one of the 3 SAO is 

 about one-tliird of the distance from the posterior one and lowered 

 enough so that the three form a wide anteriorly facing angle. The AO 

 are in a single series that is well separated from the PRC. All the 

 photophores are on the same level. There are 2 PRC; the posterior 

 one is sUghtly more dorsal than the anterior one. Luminescent 

 scales are found above or below the caudal peduncle on the larger 

 specimens, but not in both places on the same specimen. There are 

 no antorbital or suborbital luminescent organs; no photophores 

 above the lateral line ; and no POL. 



Remarks. — Myctophum oculeum is most closely related to that group 

 of species of the genus that have no photophores above the lateral 

 line, no POL, with the AO in one single continuous series, and with 

 the PLO at or below the base of the pectoral fin. This gi'oup consists 

 of M. parallelum, M. arcticum, M. rissoi, M. anderssoni, M. antarc- 

 ticum, and M. subasperum. In the following sentences, the characters 

 given for these species are taken from Parr (1928) unless otherwise 

 noted. From M. parallelum this species is differentiated by the first 

 two SAO and the two PRC not being separated by conspicuously 

 \vider interspaces as in the former; the head is included 2.6 to 3.1 in 

 the length without caudal instead of 4.0; the AO are generally less 

 than 18 (in only one specimen out of 38 are there 18 AO) while in 

 M. %urallelum the AO are 18; the eyes are not telescopic, and the lens 



