Cut and polished ammonite
Ammonites were shelled cephalopods that died out about 66 million years ago. Fossils of them are found all around the world and vary enormously in size.
These ammonites have been cut and polished so the structure of the buoyancy chambers can be more easily seen. Each one is unique so the ammonite you order may not look like the image.
Dimensions approx.: 4 x 3cm but some will be larger and a few may be smaller.