A very fine example of a fossilized ammonite (Hoploscathite). Although the shell itself has not been preserved, the internal nacre has survived, giving the opalescent 'mother of pearl' coating. Ammonites were a subclass of marine mollusks, which had a well-defined head with tentacles for feeding. They first appeared in the Lower Devonian period (400 million years Before Present), becoming extinct by the Upper Cretaceous period (65 million years BP). (1991)