44 
SHELL GALLERY. 
Fig. 38. 
inches in length, which is more or less enclosed in a thin shelly tube 
or sheath. The true bivalved shell is at the thicker end, and pro- 
Fig. 37. tects the month, labial palps, the liver, and 
other internal organs. At the opposite, or 
more slender, end of the animal, the mantle 
is produced into two small tubes, one of which 
conveys the water to the gills, whilst through 
the other the water is expelled, charged with 
the woody pulp excavated by the foot. At 
the end there is a pair of pallets, or paddles 
as they are sometimes 
termed, which are probably 
used as a means of defence, 
in closing the shelly tube 
after the contraction of the 
siphons. 
tj .J These animals are most 
/ / destructive to ships, piers, 
I I etc. ; and wood, which is 
not protected by metal, 
when once attacked, is 
soon riddled through and 
through. They work either 
with or across the grain, 
and although the holes 
may be all but touching, 
they seldom appear to run 
into oue another. 
The " Watering - pot 
shell" (Brechites), of the 
family Clavagellidce, is a 
very remarkable structure, 
and unlike the shell of an 
ordinary bivalved mollusc. 
On looking carefully, however, near the per- 
forated end (the rose), two small valves will 
be seen imbedded in the surface. They are 
found with the rose downwards buried in mud 
or sand at low water on the shores of the Indian and Pacific 
Oceans. 
t "'. 
Ship-worm 
(Teredo norvegica). 
Case 202. 
a, animal, removed 
from its shelly tube : 
p, p, pallets ; s, ex- 
halant siphon ; s', in- 
halant siphon. 
b, c, different aspects 
of the shell. 
Watering-pot Shell 
(Brechites vaginifer). 
Case 204. 
a, bivalve shell of 
the very young 
animal. 
