356 The Grayling and the Smelt 
Largely from Danish merchant-vessels, Dr. Litken 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 
Fic. 262.—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 (d’thoprora) there is a large luminous 
gland on the end of the short snout, like the headlight of an 
Fie 268 —Lantern-fish, Ceratoscopelus madeirensis (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. 
Chirothricide.—The remarkable extinct family of Chiro- 
thricide may be related to the Synodontide, or Myctophide. 
In this group the teeth are feeble, the paired fins much 
