Agastric shield is an organ in the digestive tract ofbivalves,tusk shells, and somegastropods against which acrystalline style typically rotates, in an action resembling that of amortar and pestle. The gastric shield is permeated by microcanals which transmit digestive enzymes from the stomach, and serves to protect the cells of the stomach lining from the abrasive effects of the style.[1]