The Grayling and the Smelt 133 



Largely from Danish merchant- vessels, Dr. Liitken has obtained 

 the unrivaled collection of these sea-waifs preserved in the 

 Museum of the University of Copenhagen. The species are 

 all small in size and feeble in structure, the prey of the larger 



FIG. 93. Lantern-fish, Myctophum opalinum Goode & Bean. Gulf Stream. 



fishes of the depths, from which their lantern-like spots and 

 large eyes help them to escape. The numerous species are now 

 ranged in about fifteen genera, although earlier writers placed 

 them all in a single genus Myctophum (Scopelus). 



In the genus Diaphus (^Ethoprora) there is a large luminous 

 gland on the end of the short snout, like the headlight of an 



FIG. 94. Lantern-fish, Ceratoscopelus niadeirensis (Lowe). Gulf Stream. 



engine. In Dasyscopelus the scales are spinescent, but in most of 

 the genera, as in Myctophum, the scales are cycloid and caducous, 

 falling at the touch. In Diaphus the luminous spots are crossed 

 by a septum giving them the form of the Greek letter (theta) . 

 One of the commonest species is Myctophum humboldti. 



Chirothricidae. The remarkable extinct family of Chiro- 

 thricidcB may be related to the Synodontida , or Myctophidce. 

 In this group the teeth are feeble, the paired fins much 



