FISHES. 283 



The natural colour of this species is silver- white and 

 blue ; the iris silvery, with yellow stains ; but, when 

 taken from the water, or soon after death, the entire 

 surface of the fish assumes a gilded or brassy hue. 

 When hooked, they make a loud chattering noise, ap- 

 parently produced by the passage of air through the 

 gills. We captured many examples on the rocky coast 

 of Juan Fernandez ; and also on the Equator, in long. 

 139 E., where they were attending a log of drift-wood. 

 Their flesh is wholesome but coarse. They obtain 

 from sailors their trivial name, Rudder-fish, from a 

 habit they have of swimming astern of ships. 



THE YELLOW-TAIL. 



(Elagatis Bipinnulatus, N. Sp.) 



Branchiostegous rays seven ; first dorsal, six, all spi- 

 nous ; second, twenty-six ; pectoral, twenty ; ventral, 

 six ; anal, eighteen ; a single minute spine in front of 

 the anal fin ; one spurious fin above, and a second be- 

 neath the tail, each composed of two articulated rays ; 

 jaws armed with many rows of small teeth. 



Body cylindrical ; colour of the back, blue with a 

 yellow tinge; abdomen silvery; a broad yellow line 

 extends from the snout to the tail ; caudal-fin yellow ; 

 iris silvery. 



