2.75" Tall X 4" Wide X 3/8" Deep Approx. 3.4 oz. Fossils of Fish on Rock occur in great abundance within the beds of what was once fossil lake Uinta, now part of the Green River Shale formation of Western Wyoming. Sometime during the Eocene Epoch of geologic time (50,000,000 years ago) volcanic or climatic changes probably occured which disrupted the lakes ecology and created massive fish mortality. Several species occur, among them Knightia alta, k. eocaena, and Diplomystus analis.