590 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



The terminology used for the groups of photophores is presented 

 in figures 1 and 2, on pages 588-589. 



Each fin ray that has a separate base was counted, and all rudiments 

 of gill rakers were counted on the first gill arch. 



Radiographs were expertly made by Robert H. Kanazawa and 

 T. John Leppi for the various genera and species of this family, and 

 from those films the number of vertebrae are recorded in table 1, p. 591. 



Gill (Proc. U.S. Nat. Mus., vol. 7, pp. 349-351, 1884) gives the 

 relationships among the genera and a list of the family and sub- 

 family synonymy. Gregory and Conrad (Copeia, No. 1, p. 27, 1936) 

 discuss the relationships of the family Sternoptychidae with other 

 forms. Wilimovsky (Copeia, No. 3, pp. 247-248, 1951) corrects the 

 spelling of the family name. Hubbs (Copeia, No. 2, p. 97, 1953) 

 thinks, as did earlier authors, that the family Sternoptychidae should be 

 expanded to include Gonostomatinae and the Maurolicinae. Not 

 having studied all the fishes in those relationships, I tentatively 

 assign to the Sternoptychidae those genera with a dorsal blade, exter- 

 nally visible and in front of the soft dorsal fin. 



Family Sternoptychidae 



The marine silver hatchetfishes, family Sternoptychidae, may be 

 distinguished as a group by the dorsal blade, which represents the 

 highly specialized dorsal pterygiophores, externally evident in front of 

 the dorsal fin. These pterygiophores may be fused into a thin plate 

 as in Argyropelecus, a small pair of bony keels as in Polyipnus, or a 

 single elongate spine as in Sternoptyx. Body thin, compressed, its 

 depth very great; abdominal vertebrae 11, caudal vertebrae 17 to 29; 

 branched caudal rays 9 + 8 ; scales probably present, very thin. The 

 scales are usually lost in preservation, so that they are seldom seen, 

 and thus from museum specimens no evaluation of their significance 

 is possible. 



The sternoptychids are deep-sea fishes with groups of characteristi- 

 cally arranged photophores for each genus, as are illustrated in the 

 figures beginning on p. 623. They are caught in the open sea in plank- 

 ton nets, trawls, and other gear in all temperate and tropical seas from 

 the surface to considerable depths. Records from the Pacific indicate 

 depths of 16,200 feet and from the Atlantic 12,704 feet. Such depths, 

 however, are inadequately documented because closing nets were 

 seldom used in oceanographic exploration. The fish could have been 

 caught somewhere between the surface and the deepest point reached 

 by the equipment. 



The present study recognizes 9 species and 3 subspecies for Argyro- 

 pelecus, 1 species for Sternoptyx, and 12 species and 2 subspecies for 

 Polyipnus. 



