Fossils are the remains of ancient creatures and their activity-traces in stratum, emerged in Geologic Time before Hunan History. Fossils formation depends primarily on two factors of biological and geological environment. They apt to save as fossils if biological hard parts are made up of minerals, such as various shells of invertebrates, bones of vertebrates and so on. Conversely, soft parts are not easy saved as fossils. Favorable geological environment means the remains can quickly buried through sedimentation, protecting them from biological, mechanical and chemical damage.