SHIP-WORM. 
599 
be rather more particular in our description of the 
shell, and its inhabitant, than we have hitherto been 
with the testaceous animals. 
Mr. Montague, to whose account we are chiefly 
indebted for what follows, describes the shell as 
thin, brittle, and flexuous. It is of a whitish 
colour, and becomes thick and strong towards the 
smaller end. The aperture is round, and the head 
of the animal is covered by two testaceous hemi- 
spherical valves, partly projecting in a sharp angle, 
and striated in a longitudinal direction with great 
regularity. The inside of each valve is furnished 
with a long, flat, and curved tooth. Near the ex- 
tremity of the tail of the animal are fixed two lan- 
ceolate plates, or valves, one on each side; the 
office of which is to close the extremity of the tube 
at the thickened part. “ These,” says Mr. Montague, 
u seem to be properly the shells of the animal, 
being attached to it. The tubular testaceous case, 
or sheath, which lines the hole made by this animal 
in wood, though necessary to its existence, appears 
only to be formed as an apartment in which it may 
move with ease and security ; for it is observable 
that no two tubes ever touch each other, although 
the lamina of wood between them is frequently not 
thicker than paper. The tube is seldom so long as 
the animal, as the anterior part of the perforation 
is usually not lined with it for two inches or more ; 
the smaller end is always even with the surface of 
the timber perforated, but so small as not easily to 
