The _Chitons_ differ so much from all other shell-bearing animals in
the arrangement of their shelly covering, that they have been placed
by different naturalists in various parts of their system. Lamarck,
in referring to these animals, has placed them near the end of the
Mollusca.
[Illustration: _Chiton squamosus._]
“Although,” says Lamarck, “when we examine this creature, and observe
the several pieces of which its shell is composed, attached to the
marginal membrane of the mantle which surrounds them, it appears not
a univalve, but a multivalve shell; yet these shelly pieces ought not
to be regarded in any other light than as a lengthened shell of one
piece, which Nature had originally broken transversely into several
distinct moveable pieces, to give greater freedom to the animal in its
movements.”
The Chitons, like the neighbouring genera, frequent the rocks between
high and low water mark, but are much more active in their movements.
Poli, a learned Neapolitan, in describing the anatomy of a Chiton,
says, that the interior of the mouth or throat of this animal is
covered with a multitude of teeth,—some simple, and others with three
points, and that these teeth are disposed in numerous longitudinal rows.