BORERS. Pied 
Indurated mud, clay, and wood are perforated by 
these animals as well as stone, and their boring 
habits render them objects of painful anxiety to 
those who are interested in submarine works. 
The ship-worm (7Zeredo), whose terrible ravages 
have been already alluded to (see ante, p: 41), is a 
member of this family, though the great elonga- 
tion of its body, the minuteness of its valves, and 
the shelly tube with which it lines its burrow, 
long caused it to be associated with the Worms 
(Annelida), rather than with the Mollusca. 
The fullest and most carefully prepared account 
of the natural history of this animal was communi- 
cated by Mr. W. Thompson to the Edinburgh 
New Philosophical Journal, from which paper the 
following interesting details of one of our British 
species (of which we have unfortunately no fewer 
than six) are extracted :-— 
“ The greatest diameter of the testaceous tube 
or case, at the larger end, is seven-eighths of an 
inch ; at the smaller, it varies from one and a half 
to two lines. All of the specimens have from one 
and a half to two inches and upwards of the smaller 
end of the tube greatly contracted within by 
lamine, also the partition producing the double 
aperture extending but a few lines from the very 
extremity. ‘The greatest thickness of the shell 1s 
at the smaller end, where, at the commencement 
of the lamin, its consistence is from one-twentieth 
to one-fortieth part of an inch: from this it becomes 
gradually thinner towards the greater end, which 
in the very largest specimens is found to be closed. 
up, but in several others there is no deposition 
whatever of testaceous matter for some distance 
from the termination of the cell. In one perfora- 
