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

与其他软体动物不同,壳贝缺乏齿舌,具有瓣,可将物由鳃送到口部.

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，上为一条窄横片，下为一小片（下须发达）。