This fossil is a kind of burrowing sea urchin that is now extinct - the flattened, heart-like shape allows it to burrow through the sediment more easily than domed urchins. Tube feet would have protruded through perforations in the five radiating grooves that can just be seen on this specimen. They were moved by pumping water in and out. Interestingly, urchins of this genus and have evolved so rapidly and are so common in the Cretaceous chalk formations along the south coast of England such as the White Cliffs of Dover in Kent, they can be used to accurately date the rocks.
This object is not on display.