82 MEMOIRS OF THE CARNEGIE MUSEUM 



3. Suprapectoral lower, equidistant from pectoral base and lateral line 

 (distance from lateral line half its distance from pectoral base in M. fibulatum). 



4. Upper preopercular spot on level of middle of eye (on level of lower 

 margin of eye in M. fibulatimi) . 



5. Upper supra-anal and the posterolateral separated from lateral line by a 

 space equal to their own diameter (almost touching the lateral line in M. 

 fibulatum). In both species, the upper precaudal fails to touch the lateral line. 



6. The elevated second ventral is over the middle of the interspace between 

 the first and third ventral (almost vertically above the first ventral in M. 

 fibulatum) . 



In addition to these characters, the eye in M. pterotum is much smaller and 

 has constantly a round peculiarly contracted pupil, while in M. fibulatum, the 

 eye is larger and the pupil is large and ovate in shape, the major axis passing 

 from above downwards and backwards, and the upper portion of the iris is 

 darkly pigmented while the lower half is silvery. In M. pterotum, the opercle 

 terminates in a long tongue-shaped process, which covers the suprapectoral 

 photophore and extends above the pectoral fin and beyond its base. This 

 process is not present in M. fibulatum. The latter is a larger species, reaching 

 a length of at least 100 mm. The mature female develops a single luminous 

 scale on the back of the caudal peduncle, the male may develop two. 



In Japanese specimens of M. pterotum, the prevailing number of anal 

 photophores is 6 -|- 4, this number occurring on both sides of fifty-six of the 

 sixty-five individuals, and on one side of four others. Total combinations are 

 5 + 4 (2), 5 + 5 (7), 6 + 3 (2), 6 + 4 (116), and 6 + 5 (3). 



The antero-anals are always in a curved line, the first much nearer the 

 anal base than the others, the first and second more widely spaced than the 

 following. 



11. Myctophum suborbitale sp. nov. 



Type 17 mm. long to base of caudal fin, from Station 5064, in Suruga Bay; 

 taken in open intermediate net down to 300 fathoms. 



Closely allied to M. pterotum and M. fibulatuyn, but differing from these 

 and all other species of the genus in the presence of a small round photophore 

 on the cheek below the posterior portion of the eye. 



Measurements in hundredths of length without the caudal fin: Length of 

 head 35; diameter of eye 13; length of snout 5.5; length of maxillary 23; 

 depth of body 25; of caudal peduncle 8; predorsal length 55; length of dorsal 

 base 18; pre-anal length 60; length of anal base 28; length of pectoral fin 32. 



