A cut and polished fossil ammonite from Madagascar. The individual chambers of the shell can be seen really clearly. It is discreetly and permanently attached to a clear plastic stand.
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.
5/8 inch (1.6 cm) wide, 7/16 inch (1.1 cm) deep and 1/2 inch (1.3 cm) tall.