78 MEMOIRS OF THE CARNEGIE MUSEUM 



largest, 20 mm. in length, has no trace of luminous plates on the caudal pe- 

 duncle. The material has been directly compared with specimens from the 

 eastern Pacific and no difference found. Young individuals of Dasyscopelus 

 orientalis from the same region must be carefully distinguished. A specimen of 

 the latter, 28 mm. long, has the scales without trace of spines. The number and 

 distribution of the photophores are the same, but the eye in D. orientalis is 

 larger, the photophores themselves are larger, there is a preorbital below the 

 nostril more conspicuous than the one above, the lower subpectoral is decidedly 

 below the level of the upper, the second ventral is not more elevated than the 

 others and the precaudals are closely crowded. In M. laternatum, the first 

 ventrals are closely apposed, the second far out at the sides, the third and 

 fourth intermediate in position; the precaudals are much more widely separated 

 than the postero-anals. 



7. Myctophum calif orniense Eigenmann and Eigenmann. 

 Mydophum californiense Eigenmann and Eigenmann, West. Amer. Sci., 1889, 



p. 124; San Diego, Cal. 



A single adult male, 127 mm. long, from Station 5034, south of Nemuoro, 

 Hokkaido (43° 05' 30" N., 145° 57' 40" E.); and two adult females of the same 

 size from Sagami Bay (C. M. No. 4607). 



This species usuall}'^ has been considered identical with M. himiboldti, but 

 examination of the type and a cotype of californiense from San Diego, of a 

 third specimen from off the coast of Lower California, and the three specimens 

 here recorded from Japan, shows agreement in a combination of minor char- 

 acters which indicate specific difference from humboldti. These characters are as 

 follows : 



1. Pectoral rays 17 or 18 (12 to 14 in humboldti). 



2. Entire back of caudal peduncle in adult males covered by a series of 

 distinct luminous plates, each of which is surrounded by black pigment and 

 separated from the adjoining plates. The series contains six large plates and 

 may in addition contain one or two minute ones immediately behind the adi- 

 pose. These are present in the type of the species and in one of the Japanese 

 specimens. In M. humboldti, there are never more than one or two small in- 

 conspicuous plates on the back of the caudal peduncle. In the adult females 

 from Japan, there are seven or eight distinct plates covering the area between 

 the anal fin and the caudal. 



3. The line of the antero-anals is nearly or entirely straight, while in 



