I keep finding small rocks at the base of banks alongside the road, around the area where I live in Bath, UK. Most of them contain bivalves but I keep coming across this shape which I can’t recognise (picture 1)
Picture 2 is a close-up of rock A which seems least weathered.
I think these are the imprints left behind by something but I also have an example of what I think could be the actual object itself (please excuse my lack of terminology!) but it’s tiny compared to the other three examples (picture 3)
Any help with this would be great thanks.