SCOPELID^. 585 



below the anterior dorsal rays. Dorsal fin nearly in the middle 

 of the length of the body ; adipose fin small ; anal generally 

 long ; caudal forked. Branch iostegals from eight to ten. 



The fishes of this genus are small, of truly pelagic habits, 

 and distributed over all the temperate and tropical seas ; 

 they are so numerous that the surface-net, when used during 

 a night of moderate weather, scarcely ever fails to enclose 

 some specimens. They come to the surface at night only ; 

 during the day and in very rough weather they descend to 

 depths where they are safe from sunlight or the agitation of 

 the, water. Some species never rise to the surface ; indeed, 

 Scopeli have been brought up in the dredge from almost any 

 depth to 2500 fathoms. Thirty species are known. Gymno- 

 scopelus differs from Scopelus in lacking scales. 



IpnoI'S. — Body elongate, sub-cylindrical, covered with large, 

 thin, deciduous scales, and without phosphorescent organs. Head 

 depressed, with broad, long, spatulate snout, the whole upper 

 surface of which is occupied by a most peculiar organ of vision 

 (or luminosity), longitudinally divided in two symmetrical halves. 

 Bones of the head well ossified. Mouth wide, with the lower 

 jaw projecting; maxillary dilated behind. Both jaws with 

 narrow bands of villiform teeth; palate toothless. Pectoral 

 and ventral fins well developed, and, owing to the shortness of 

 the trunk, close together. Dorsal fin at a short distance behind 

 the vent ; adipose fin none ; anal fin moderately long ; caudal 

 subtruncated. Pseudobranchise none. 



This singular genus, one of the " Challenger " discoveries, 

 is known from four examples, obtained at depths varying 

 between 1600 and 2150 fathoms, off the coast of Brazil, near 

 Tristan d'Acunha and north of Celebes. All belong to one 

 species, I. mv/rrayi. The eye seems to have lost its function 

 of vision and assumed that of producing light. The speci- 

 mens are from 4 to 5J inches long. 



Paealepis. — Head and body elongate, compressed, covered 

 with deciduous scales. Cleft of the mouth very wide ; maxillary 



