Description: The Fort Union Formation comes from the first geological epoch to follow the extinction of the dinosaurs. The Fort Union Formation covers much of Montana, eastern Wyoming, and the western Dakotas. It contains an extensive amount of minable coal, and has an extensive flora. It was a flora indicative of a lowland, sub-tropical to temperate climate. The depositional environment was both fluvial and lacustrine, with the fluvial deposits holding the most coal. These gastropod shells were found in a location near that of the plants I have posted (see my other listings). Interestingly, they are typically not found in the exact same location due to the acidic environment that decaying plant material would impart. They are often found free of matrix such as these, allowing you to study them from every aspect. This is a good pair of examples of this freshwater taxon.