Geologic Era: Eocene
Location Discovered: Wyoming (Green River Formation)
Size: Up to 5 centimeters long
Estimated Range: Wyoming, Utah, Colorado
Extinction: Roughly 46 million years ago
Specimens like this were ( and still often are) called turritella agate, though this name is incorrect. These shells were deposited on the shores of large, Eocene era lakes. The genus Elimia is still around today, but this particular species is extinct. In life, these were tiny aquatic snails. Elimia would have shared its watery home with a variety of fish, birds, and crocodiles.
Modern Elimia shell: By USGS – Elimia virginica https://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1032 Downloaded 29 October 2008, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5095398