Here are a few more Rudists from France. This is a Radiolites trigeri from the Cretaceous (Turonien) near Charente, France.You can see the thick exterior walls surrounding the hollow area where the body would have been. Now it's full of Calcite crystals.
A side view showing the full length and depth of the specimen. This fossil represents the base and a portion of the full shell but is not complete top to bottom.
A close up of the Calcite crystals within the body chamber.
This is a portion of a rudist called Hippurites. It's a much smaller fossil than the above specimen and I'm not sure if it is a cast of the body chamber or a portion of the external shell.
Thanks to Gery for sending me these fossils.