262 MALACOPTERYGII. — PLEURONECTID^. 



sandy or muddy shores, and unprovided with 

 swimming-bladders, their place is close to the 

 ground, where, hiding their bodies horizontally 

 in the loose soil at the bottom, with the head 

 only slightly elevated, an eye on the under side 

 of the head would be useless ; but both eyes 

 placed on the upper surface afford them an 

 extensive range of view in those various direc- 

 tions in which they may either endeavour to find 

 suitable food, or avoid dangerous enemies. Light, 

 one great cause of colour, strikes on the upper 

 surface only ; the under surface, like- that of 







■'%. 



UPPER SIDE OF THE SOLE. 



most other fishes, remains perfectly colourless. 

 Having little or no means of defence, had their 

 colour been placed only above the lateral line on 

 each side, in whatever position they moved, their 

 piebald appearance would have rendered them 

 conspicuous objects to all their enemies. When 

 near the ground, they swim slowly, maintaining 



