Unlike other molluscs, bivalves lack a radula and feature labial palps, which carry food from the gills to the mouth.

与其他软体同的是,双壳贝缺乏齿舌,具有唇瓣,可将由鳃送到口部.

The mandibles are usually lost, the labrum is reduced to a narrow transverse sclerite, and the labium is a small flap ( though its palps retain quite large).

上颚消失，上唇退化为横片，下唇退化为小片（下唇须发达）。