This shell is possibly Plagiostoma subcardiiforme which would ‘fit’ the rock which is Forest Marble. This hard, shelly limestone is essentially a fossilised beach composed of shells washed up on the shore on the edge of a shallow sea. Forest Marble is also known locally as Bothenhampton Stone and was once quarried as a building material. It is used in many of the more prestigious buildings around Bridport and also as the footings for buildings such as stables as it provided a damp-proof stone in the days before damp-proofing membranes were available.
Find out more about bivalves on the molluscs pages.