Hello, I've been a follower of your channel for years now and I really enjoy your content. I was surprised by the "mysterious" shellfish because it looks like one that is very common on the coasts of my country, France. I did some research and it seems to be a smooth clam, "callista chione". It's a common shell on the european atlantic coast and Mediterranean. I guess it might have been brought there by a trade ship. 😊