The word Polyplacophora is derived from three Greek words poly=many, placo=plate and pherein=bearing. Thus this class includes animals which have many plates. This class has two orders which are named as follow
a) Order1:-Lepidopleurida
b) Order2:- Chitonina
The characteristics are listed as below.
1) They are mostly bilaterally symmetrical, dorsoventrally flattened mollusks.
2) They have elliptical, convex dorsally and flattened ventrally body.
3) They have distinct head without eyes and tentacles.
4) They have shell composed of a longitudinal series of eight calcareous pieces.
5) They have foot flat and ventral ,laterally bordered by a groove containing gills.
6) They have well developed radula having 17 teeth.
7) They have coiled intestine with a terminal anus.
8) They have a pair of nephridia extending from pericardium to the lateral groove.
9) They have a pair of gonoducts without relation to the pericardium.
10 ) They have sex organs in two separate body(dioecious).
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