Diplodonta astartea (Nyst, 1835)

This clean, perfectly circular clam represents a highly sophisticated way of living in oxygen-poor sediments. It used a specialized, highly extendable foot to construct temporary, mucus-lined ventilation tubes directly from its burial depth up to the open water. Finding these smooth, beautifully rounded shells points toward clean, well-oxygenated fine sand horizons where sub-surface life was highly organized.