hi all, here's another couple of the same species from down my way of the west coast of France. From the same site as my previous Oxycerites orbis & Oppelia aspidoides , therefore Bathonien unless you use Phil's timeline where they'd be from last weekend !
The good one is 100mm, 10cm, 0.1m or 4" in dia & exactly how it popped from a big rock. The other with the centre whorls missing has been hacked to free the calcite middle, as the rest were mashed, but it turned out that the centre had already gone . The backside was eroded out & home to a rather large hidden ragworm
Now it's your go Phil to tell me what it is as it ain't in me book !