266 
TIMBER 
most destructive at about low water level. In Hartlepool, 
where the North Eastern Eailway Company have timber 
ponds for the storage of the large timber trade of that port, 
fresh water has to be pumped in to keep it below that degree 
of saltness which enables the animal to live. The limnoria 
will attack knots, but prefers softer wood, and it is curious 
to see in worm-eaten wood how this hard ]3ortion stands 
out in relief when the rest of the timber is eaten. 
The Chelura Terebrans resembles the ordinary shrimp, is 
very different in appearance to the limnoria, though about 
the same size or somewhat larger. It swims on its back, 
and is a jumper ; its burrow, also, affords both residence 
and food. It attacks the wood entirely from without, 
reducing it to minute fragments by means of a kind of 
file ; attacking it in any part, but preferring the softer parts. 
Specimens one- third of an inch long have been measured. 
None of these pests will, so far as the author's experience 
goes, exist in sewage-laden water ; some will not exist in 
muddy waters, and they are most destructive in clear, warm, 
pure sea water. 
The Sphaeroma is another of these timber destroying 
animals found in Australian and United States waters. 
It is rather larger than the limnoria, and simply erodes 
the surface of the wood and by this means often discloses 
the ravages of the teredo. Unlike the others, however, it is 
active in comparatively fresh water. 
The Pholas, which is very similar in appearance to the 
common mussel, and is a prized shell fish for food on tbe 
shores of the Mediterranean, generally prefers boring in 
stone, but there is no doubt that in some situations in the 
tropics it also attacks wood. It bores at right angles to 
