YAKRELL ON FLAT-FISHES. 107 



us hear what Yarrell says on these strange modifica- 

 tions. " The Mat-fishes . . . are, by this depressed 

 form of body, admirably adapted to inhabit the lowest 

 position, and where they occupy the least space, among 

 their kindred fishes. Preferring sandy or muddy shores, 

 and unprovided with swimming-bladders, their place 

 is close to the ground, where, hiding their bodies hori- 

 zontally 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 directions 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 

 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 appear- 

 ance would have rendered them conspicuous objects to 

 all their enemies. When near the ground they swim 

 slowly, maintaining their horizontal position ; and the 

 smaller pectoral and ventral fins on the under side are 

 advantageous where there is so much less 'room for their 

 action, than with the larger fins that are above. When 

 suddenly disturbed, they sometimes make a rapid shoot. 



