�y��vlog

The Anatinidæ have thin, often inequivalve pearly shells.

A bivalve is said to be equivalve when the two shells composing it are of the same size, inequivalve when they are not.

For instance, Professor Hutton describes a certain shell as "thick, irregular, sharp ribbed, with the margin dentated or lobed, very inequivalve; upper valve opercular, compressed, wrinkled, with thick concentric laminae; lower valve cucullated, purple, white within, edged with purple or black; lateral margins denticulated; hinge generally attenuated, produced, pointed."