BIVALVE MOLLUSC AN S. 243 



amongst other matters he observed, that from 

 some alteration in the sands of that coast the 

 number of small shell fish had considerably 

 diminished of late years, which being the prin- 

 cipal food of soles and other flat fish had occa- 

 sioned a great diminution of them also. An 

 over abundance of burrowing bivalves may 

 undermine the beach to that degree, that the 

 sea in high tides and stormy weather may make 

 such a breach upon it as may carry away, or 

 bury too deep, a large proportion of these shell 

 fish, which would cause the fishes to leave the 

 coast for one better provided with food for them. 

 No animal has been more celebrated for the 

 mischief it has occasioned as a timber-borer than 

 that of which I shall next give some account. 

 I am speaking of the ship-worm. 1 Though the 

 animal of some of the land-shells, as the snails, 2 do 

 him some injury in his garden, man seldom suffers 

 very materially from their ravages, but the ship- 

 worm, where it gets head, does him incalculable 

 injury : destroying piles as far as they are under 

 the water and every thing constructed of timber 

 that is placed within their reach, to which they 

 are as injurious as the boring wood-louse ; 3 

 they even attack the stoutest vessels, and render 

 them unfit for service. Their object however is 

 not to devour the timber, but with the same view 

 that the pholads bore into the rock, to make 



1 Teredo navalis. 2 Helix. 3 Limnoria terebrans. 



