42 MARKETABLE BRITISH MARINE FISHES 



sharks which occur frequently in British waters. With respect 

 to their bodily peculiarities they all belong to one family, 

 having a stout thick form with the second dorsal fin and the 

 ventral fin of small size and opposite to one another. The 

 porbeagle, which is frequently taken in summer by the Cornish 

 fishermen, has long pointed teeth, and a keel on each side of its 

 tail. Its length is from three to eight feet. The thrasher is 

 conspicuously distinguished by the extraordinary length of the 

 upper lobe of the tail, which is as long as the rest of the body. 

 This tail is said to be used for beating whales, but it is certain 

 that this shark feeds upon herrings, mackerel, and other 

 gregarious fishes, and it seems probable that it swims round a 

 shoal of these fishes and lashes about with its tail in order to 

 keep them crowded together and prevent them from escaping. 

 The basking .shark is of very large size, reaching twenty-five to 

 thirty feet in length. Its snout ends in a peculiar cylindrical 

 projection. Its teeth are small and conical, and it has numerous 

 long projections on its gill-bars which form a straining apparatus. 

 These projections are called gill-rakers, and resemble those of 

 the herring and other bony fishes, serving, as in these fishes, to 

 strain from the water that is passed through the gill openings 

 the multitudes of minute Crustacea and other creatures which it 

 contains. This large shark therefore, like the huge whale and 

 the small herring, is nourished entirely by extremely minute 

 forms of life. It visits the west coast of Ireland annually in 

 considerable numbers, and is regularly hunted for the sake of 

 the oil obtained from its liver. It has the habit of lying motion- 

 less at the surface of the sea, and as it is not easily alarmed the 

 fishermen approach it in a boat and harpoon it. The fishery is 

 chiefly practised off the Achill and Boffin Islands. 



The peculiar form of skates and rays as compared with dog- 

 fishes is connected with their habit of resting continually and 

 concealing themselves on sandy or gravelly ground. In this 

 respect they differ from dog-fishes as flat-fishes such as plaice 

 and turbot differ from round fishes such as cod or haddock. 

 But the mode of flattening in the two cases is as different as it 

 possibly could be, the difference being that the lower surface in 

 the skate is the belly, in the flat-fish the left or right side. 

 Accordingly, if the skate is divided down the middle line of the 

 upper surface the two halves will be exactly similar, whereas if 



