The order of the bivalves is a very large and important one.
These, of course, are closely connected with the land shells, which the bivalves are not.
The first two include Univalves and Bivalves, the last only Univalves.
Oysters, clams, and other bivalves have their eyes along the edge of the shell.
All the mollusca, except the bivalves, are provided with this radula.