This fossil ammonite has been cut in half and then polished, so that you can see the internal structure of chambers, now filled with minerals. This ammonite comes from Madagascar and is discreetly and permanently attached to a clear plastic support.
Ammonites are extinct relatives of modern day nautiloids and squid. The largest known ammonite in the world would have been 8 1/2 feet (2.59 metres) across if it were complete.
3/4 inch (1.9 cm) wide, 3/8 inch (0.95 cm) deep and 5/8 inch (1.6 cm) tall.