Another type of bivalve steinkern from the British Jurassic has been called a bull's heart. Like 'Osses 'Eds, these were found by Robert Plot at Headington, who referred to them as 'Bucardites'. They are now known by the scientific name Protocardia . Their resemblance to a heart becomes apparent when the fossils are viewed from the side, with the mould of the left valve on one side and that of the right valve on the other.
Evidence that fossils of the same type have long been known to humankind comes from the discovery of a Protocardia steinkern in a Bronze Age barrow (burial mound) at Aldbourne in Wiltshire (Oakley 1974). This barrow was built on the Chalk and yet the fossil comes from an older Cretaceous formation, the Upper Greensand, and must have been collected and taken to the site of the barrow.