LIMNORIA LIGNORUM. 353 



to drag itself along. It turns rapidly, using chiefly the 

 caudal plates, which it uses as oars ; sometimes also it 

 propels itself by a sudden movement of the tail, back- 

 wards, to the distance of an inch or more, through the 

 water. 



It appears that, notwithstanding the extent and im- 

 portance of its ravages upon structures, affecting the 

 interests of mankind in a very extensive manner, it was 

 not noticed until about the year 1811, when Dr. Leach 

 announced it, as a new and highly interesting species, 

 sent to him by Robert Stevenson, Esq., the celebrated 

 engineer, and as occurring in the greatest abundance at 

 the Bell Rock lighthouse on the Scotch coast, erected 

 by that gentleman, burrowing into the old woodwork, 

 which it perforated in a most alarming manner, entering 

 into it to the depth of several inches by boring in every 

 direction, generally in straight lines, avoiding, however, 

 the knots of the timber, round which it works. 



Many kinds of wood, including old oak, are devoured 

 by the Limnoria, although it was generally found in other 

 timbers, especially Memel fir. Mr. Stevenson saw it 

 attack oak, black-birch, and other woods ; indeed, teak 

 was the only wood exposed to its ravages which was not 

 perforated. -Its mode of attack is very similar to that of 

 the common Anobium in the timber of houses, &c., which 

 is so often mistaken for dry rot, the chief difference 

 being that the action of the waves wash away the outer 

 and harder annual layers, in consequence of all the soft 

 intervening spaces being eaten away, whilst the inner 

 ones, as well as the knots of the branches, stand out 

 in relief consequently the surface of the wood soon 

 becomes gradually rotten and reduced in its dimensions. 



It is by means of its mandibles that it forms its 

 burrows in the wood, which evidently forms its support, 



VOL. II. A A 



