PERFORATIONS OF MARINE ANIMALS. AT 
on a flat surface. Its movements in the water are very active, 
and it swims chiefly on its back. 
The second form, Limnoria lignorum (the Gribble, as it has 
been popularly called), is an Isopod,* and closely allied to 
the Spheromide, which occur in crevices of rocks, especially on 
the southern (Channel Islands) and western shores (Outer 
Hebrides). Though this form (Limnoria) must have been 
familiar to marine observers from a very early period, it was 
fully described by Dr. Leach only in 1811, when Mr. Robert 
Stephenson, the celebrated engineer, found it burrowing most 
destructively at the Bell Rock in the large beams of Memel fir 
supporting the temporary beacon in which he and his assistants 
resided. The sides of these beams had been charred and coated 
with pitch, but the ends resting on the rock had been overlooked, 
and there Limnoria began its operations. Other logs of pine 
were reduced at the rate of about an inch a year, and the house- 
timbers were so much destroyed that many stood clear of the 
rock, supported only by the iron bolts and stanchions. Since 
its ravages at the Bell Rock brought it under the notice of men 
of science it has been found very generally distributed on our 
shores from Shetland to the Channel Islands, and it is common 
in Kuropean waters. It attacks all kinds of submerged wood, 
such as piles facing the wharves, sunken wrecks, stakes of 
Salmon-nets, and indeed all unprotected wood. The late Dr. 
Coldstream, of Leith, the author of an excellent account of the 
animal, mentions that, in 1825, so extensive were the ravages 
of Limnoria that many of the piles of Trinity Chain Pier had to 
be replaced after four years’ service, and studded all over with 
broad-headed iron nails from the base to the limit of high-water 
mark. The same plan was adopted in extending the pier at 
Leith on wooden piles four years afterwards (at a cost of £1000, 
the whole pier being £30,000). At Devonport Dockyard at this 
moment it is more troublesome than the Teredo. 
Like the foregoing species, Limnoria uses its mandibles for 
burrowing, and the particles of wood are swallowed. It gener- 
ally chooses the softer places, shunning the knots and hard lines 
of wood. It even avoids the New Zealand pine (Cowdie). As 
* An elaborate and well-illustrated Report on this form was published by 
the Netherlands Commission in 1893. 
