OF THE BRITISH ISLANDS. 37 



western coast-line, that as many as ten and even twenty 

 thousand have been enclosed and brought to land at a 

 single haul of the seine. E This fish is but little valued for 

 the table. Its distinction from the common Mackerel may 

 be at once recognised by the absence of the series of 

 minute dorsal and ventral finlets in the region of the tail, 

 which characterise the last-named species, and also by the 

 presence of a row of sharp, spinous scales or plates, which 

 form a continuous series throughout the entire length of the 

 lateral line. Twenty inches represent the longest dimen- 

 sions attained by the adult Scad ; its colour is usually dull 

 blue along the back, and silvery beneath the lateral line. 

 The well-known Pilot-fish {Naucrates ductor), No. 48, is so 

 called by reason of its characteristic habit of associating 

 with various species of Sharks, which fish it is asserted to 

 swim in front of, and guide to its prey. On this account 

 it is popularly known among sailors as the " Shark's 

 provider." In illustration, however, of the fact that the 

 partnership established between the two fish is not always 

 to the advantage of the Shark, it has frequently been known 

 to entice its bulky companion to swallow a baited hook, 

 which it would otherwise have left unnoticed. The Pilot-fish, 

 like the Remora, frequently attaches itself to vessels for 

 the sake of the discharged garbage, following them with 

 such perseverance as to be often brought into harbour. On 

 one occasion two Pilot-fish were thus known to accompany 

 a sailing-vessel during a voyage of eighty days, between 

 Alexandria and Dartmouth, they having become so tame 

 on its arrival at the latter port, that they were easily 

 captured, and, it is a matter of regret, killed and eaten. 

 The Pilot-fish rarely exceeds a small Mackerel in dimensions, 

 its colour being likewise somewhat similar, consisting of a 

 bluish-grey ground, variegated by five or six broad transverse 



