1. The Precambrian systems -- 2. The Cambrian System -- 3. The Ordovician System -- 4. The Silurian System -- 5. The Devonian System -- 6. The Carboniferous System -- 7. The Permian System -- 8. The Triassic System -- 9. The Jurassic System -- 10. The Cretaceous System -- 11. The Tertiary System -- 12. The Quaternary System