Fossil shells (either large bivalves or brachiopods) in Carboniferous Limestone on the shore at Broughton Bay on the Gower Peninsula, South Wales.
https://natureinfocus.blog
?bivalves..
I just realised that I had shown these images before in 2013. In that post I said the fossils were brachiopods but cannot recall the source of the information, except that Hunts Bay Oolite is known to have brachiopods and bivalves were not mentioned. Do you have a reference?