FLAT-FISHES. 



177 



the Skagerak. It is a shallow water fish, being rarely taken in 

 depths exceeding 40 fathoms. About 70,000 cwts. of Turbot, 

 valued at £300,000, are annually landed in Britain, mostly from 



the North Sea trawling grounds. 



The Brill has the same general 



distribution as the Turbot. 



Pseudorhombus russelli, 764, is a fish widely distributed over 

 the Indian Ocean and seas of East Africa, China and Australia. 

 Closely allied to it is ParaMchthys dentatus, 765 and 766, the 

 " Flounder " of the Atlantic coast of America. In this fish the 

 middle fin-rays of the caudal fin are longer than the others, so 

 that the hind edge of the tail is not rounded, but has the form of 

 an obtuse angle. 



The genus Pleuronectes is represented by the Plaice, the 

 Flounder and the Dab. In this genus the mouth is terminal and 

 very small, the teeth are more developed on the lower side than 

 on the upper; the eyes are large and prominent, the dorsal fin 

 commences above the dorsal eye ; the scales are small and in 

 some cases rudimentary. The Plaice, Pleuronectes platessa, 767- 

 771, fig. 83 B, has uniform scales, some bright red or orange 

 spots, a lateral line nearly straight, bony tubercles on the inter- 

 orbital ridge, and a spine in front of the anal fin. The 

 Plaice is comparatively a cold water fish. It is abundant all 

 round the British and Irish coasts, on the coast of Iceland, and 

 in the White Sea. It is very rare in the Mediterranean. It 

 is taken only by the trawl, and in depths usually less than 30 or 

 35 fathoms. About 1,100,000 cwts. of Plaice, of the value of 

 £1,200,000, are landed in Britain annually. Nine-tenths of the 

 total are taken in the North Sea, where the young Plaice are 

 mostly reared along the shallow coasts of Holland, Germany, and 

 Denmark, from which they migrate off-shore as they grow older. 

 The more northern forms, e. g. those taken off Iceland, are very 

 dark in colour. 



The Flounder, Pleuronectes flesus, 774 and 775, has tubercles 

 at the bases of the fin-rays of the dorsal and anal fin ; the scales 

 are rough along the lateral line, elsewhere they are rudimentary ; 

 yellow spots are only exceptionally present. The Flounder is 

 an estuarine fish except in the spawning season, when it descends 



N 



Plaice. 



Flounder. 



