Turritella Agate

One story of this fossil is that part of Wyoming was covered by an ancient saltwater sea, and in the Cretaceous period, gastropods (snails) called Turritella made a living. They had elongated, chambered shells, which make up the pattern in this stone. However, experts in Wikipedia insist that the fossils visible in these stones are actually from a freshwater species called Elimia tenera, deposited during the Eocene epoch. Either way, the stones are fascinating and filled with ancient life.  The back of these pieces are matt-finished with more fossil shells visible.