MULTIVALVES. ol 
buoyant, as not to sink in even the most tremendous 
storms. 
The peculiar structure of the genus Chiton, the 
plait, or folded shell, readily distinguishes it from the 
preceding Multivalves. The shell is generally com- 
posed of eight pieces, called valves, and surrounded 
by a narrow belt or margin, which is sometimes 
covered with scales. But why such a different con- 
formation from that which distinguishes the testace- 
ous coatings of his relative the Pholas?) The back 
of the Chiton is alone defended by a shell; hence 
the valves are surrounded with a narrow belt, and the 
cartilages by which they are united. The animal is 
thus enabled to roll together into a ball, like the 
hedgehog or porcupine, on the approach of danger ; 
and by this ingenious expedient he is not only 
effectually protected from the attacks of his numerous 
enemies, but is, perhaps, enabled to elude their 
vigilance, from the similarity which he bears in this 
state to a pebble perforated by the waves. 
The construction of the inhabitant also differs 
essentially from that of the Pholas, or Lepas. He 
has neither eyes nor horns, because unnecessary to 
a creature that never goes beyond his shell. In 
short he resembles a well known insect, often met 
with in decayed timber; and when extracted, the 
form of the shell is not unlike a boat. 
