Bivalves
Bivalve mollusca (clams) have a shell which is composed of two separate but articulating parts. Each one of these two parts is known as a "valve".
The two valves are known as the "right valve" and the "left valve"; these are labeled with respect to the anterior end of the bivalve, when the umbones are facing upward. In many, but not all, bivalves, the two valves are more or less symmetrical and thus (other than the hinge line) look like mirror images of one another.
Read more about this topic: Valve (mollusc)
Famous quotes containing the word bivalves:
“So motionless, she seemed stone dead—just seemed:
She was too old for death, too old for life,
For as if jealous of all living forms
She had lain there before bivalves began
To catacomb their shells on western mountains.”
—Edwin John Pratt (1882–1964)