To avoid sampling bias, they restricted their analysis to one group of animals—the bivalve molluscs—that fossilise well.

为了防止取样偏颇，他们将分析对象限制在一类化石记录保存完备——双壳类软。

When the Thompson quadruplets espied him one day, they called him a bivalve and ran quickly away.

有一天，汤普森家四胞胎看见他， “双壳！”

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

与其他软不同是,双壳缺乏齿舌,具有唇瓣,可将食由鳃送到口部.