Bivalves which lack this ability, and cannot therefore be kept alive for long after being taken, include the razor clam and soft-shelled clam. These should not really be called clams at all, since they cannot ‘clam up’; see clams.
Of the bivalves which are cultured, the oyster and mussel are by far the most important. Culture of the latter has been so far developed that it is now, in terms of consumption, the most popular bivalve. Bivalves collectively constitute a major food resource and have the advantage over their companion categories in the mollusc world, the gastropods (single shells) and the cephalopods, that they are less apt to arouse feelings of distaste or revulsion. They also benefit from having in their ranks such undisputed delicacies as the oyster and scallop.