Retusa truncatulaRetusa truncatula is a species of very small head-shield sea snail or barrel-bubble snail, a marine gastropod mollusc in the family RetusidaeThe subspecies Retusa truncatula var. mammilata: is a synonym of ''Retusa mammillata''DescriptionThe shell is minute with a flattened spire and longitudinal striations. The colour of the living animal is white. The adult length is usually less than 4 mm.DistributionThis species occurs in South Africa, from False Bay to Durban in shallow estuaries. It is also known from northern Europe, the Mediterranean Sea and the Canary Islands.Natural historyThis small sea snail lives from the intertidal zone to just below the low water mark. It burrows in the mud or sand of tidal marshes, and feeds on foraminiferans.