THE FLAT-FISH FAMILY 227 



nine were molluscs, in twelve Crustacea, in four worms. The 

 molluscs were chiefly the bivalve Scrobicidaria, which is 

 common on the Lancashire coast. 



The Flounder {Pkuroiiectes fiesus). 



Distinguishing Characters. — Rough spiny tubercles in a single 

 row along the bases of the dorsal and ventral fins, and about 

 the front end of the lateral line. These are enlarged scales, 

 the other scales are small and smooth, and not projecting from 

 the skin. The head is rather large, like that of the plaice, 

 but without the tubercles on the ridge behind the eyes which 

 are present in the latter. The teeth are conical and pointed. 

 The fin rays are fewer in number than in any other species of 

 Pleuronectes, namely, dorsal 60 to 62, ventral 39 to 45. The 

 colour is a dark brown or nearly black, without distinct mark- 

 ings ; the lower side is a brilliant white. 



Size. — Dr. Fulton found that ripe males ranged in length from 



6 to 14 inches, the average being 8'5 inches ; females from 



7 to lyh inches, the average ir3 inches; the largest female, 

 mature but not ripe, was 18 inches long. 



Na7iies. — Fluke is applied to this fish as well as to plaice 

 and dab ; in Morecambe Bay it is distinguished as white fluke, 

 in Scotland as the " fresh-water fleuk." 



Habitat. — Occurs on the European coast from the Mediter- 

 ranean to the Baltic and shores of Scandinavia. In the 

 Mediterranean it is usually smooth, the tubercles not being 

 developed, while in the Baltic they are more developed than on 

 the English coast. It is not found on the American side of the 

 Atlantic or in the Pacific. 



Of all the British flat-fishes this species is the least marine 

 in its distribution. It belongs essentially to estuaries, ascending 

 into fresh water in many rivers when there are no natural or 

 artifical barriers to obstruct its passage. It is common and in 

 most estuaries abundant, and there is no estuary in the British 

 Islands in which it does not occur. However I know of no 

 instance in which it is found in fresh water cut off from com- 

 munication with the sea, unless artificially introduced ; it can 



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