ICHTHYOLOGICAL COLLECTIONS OF THE ALBATROSS. 399 



Family MYCTOPHIDiE. The Lantern Fishes. 



10. Diaphus theta Eigennuum & Eii^eumann. 



Mijctophnm protoculut^ Gilbert. Proc. U. S. Nat. Mus. 1890, 52. 



Five siiecinious from statioii 3318, taken off the coast of Califoruia near I'oiut 

 Arena, Huuiboklt County, at a depth of 45.5 fathoms. These are identical with the 

 types of M. protociihin, and are in sufficiently good state of preservation to show the 

 division of the luuiiuou-s spots, a character not visible in the types oi M. proioculus. 

 It is obvious that the spots are divided into upper and lower halves, which are 

 structurally dilferent, the narrow pigment band indicating this separation on the 

 surface. The species is now known fi'om the above locality, from Albatross station 

 3072 (otf the coast of Washington, 584 fathoms), and from the mouths of Sebasiodes 

 caught near San Diego, Cal. 



The specimens before us show great variation in the size of the subocular 

 luminous blotch, and indicate how little dei^endence can be placed on this as a 

 specific character. In addition to the roundish supra-nasal spot described by Eigen- 

 mann, the species jiossesses a more or less developed subocular bar. In one specimen 

 the latter is a hare line with a minute point separated from it posteriorly. In others 

 it is wider, in extreme specimens reaching one-third the diameter of the pupil. There 

 remains constantly separated from it the small dot already referred to. A peculiar 

 soft ilattish body, half as large as pupil, is attached by one edge to the shoulder 

 girdle just above the insertion of the pectoral lin, the other edge remaining free. It 

 is constantly in-esent and uniform in position in all specimens that have come under 

 our observation, including types of I), theta and M. protocaJus. It nuiy be a luminous 

 organ, though it has not strikingly the appearance of one, and its nature must be 

 considered problematical. 



11. Naunobrachium leucopsaruni Eigenmann. 



Numerous specimens from Alaskan waters agree entirely with those from the type 

 locality. Two very closely related species are found among these northern speci- 

 mens, and both are also present in the dredgings from the Santa Barbara Channel. 

 Both of these are found among the types of Myctopkum nannochir, and the descrip- 

 tion of the latter is partly drawn from specimens of each. Such being the case, the 

 name ininnovMr becomes available in connection with the second of these forms, to 

 which I shall here restrict it. The two species are extremely close, and immature or 

 mutilated specimens are often distiuguisliable with difficulty. The species dilier in 

 the following respects : 



LEUCUPSAEUM. 



Caudal peduncle deep, its least depth about halt' 

 that of body. 



Head short, 3§ to 3J in length. 



Maxillary shorter, the cheek wider, less taper- 

 ing posteriorly. 



Luminous iiatchcs above and below tail occu- 

 pying the whole length of caudal peduncle, in 

 rare cases somewhat shortened. 



Color lighter, the operclo usually with silvery 

 luster, the iris with silvery pigment, and the tins 

 lighter. 



Antro-anal spots usually ti. N'outral spots 4. 



NANNOCHIR. 



Caudal peduncle long and slender, its least 

 depth two-fifths to one-third that of body. 



Head longei>, 3^ to 3j in length. 



Maxillary long, the preopercle very obliquely 

 placed, thecheek long, tapering to an acute angle 

 posteriorly. 



Luminous patches on tail short, usuallj' occu- 

 pying from one-fourth to one-third length of 

 caudal peduncle, rarely longer than this. 



Color darker, the opei'dc black, the iris usually 

 without silvery and the fins uniformly black. 



Antro-anal spots usually 7. Ventral spots 

 usually 5. 



Specimens of N. leacopsanun were taken at stations 3227, 3307, 3308, 3325, 3329, 

 3343, and 3348. The first live mentioned were in Bering Sea, north of Unalaska 

 Island, at depths of 225 to 1,625 fathoms; the last two from off the coasts of 

 Washington and California, depths 516 and 455 fathoms. 



