SILURIAN 25. UPPER SILURIAN British Upper Ludlow formation, Downton sandstone, with bone-bed (p. 459). Lower Ludlow formation, with oldest known fish remains (p. 461). Wenlock limestone and shale (p. 465). Woolhope limestone and grit (p. 467). Tarannon shales (p. 468). _Beds of passage between Upper and Lower Silurian:_ Upper Llandovery, or May-hill sandstone, with _Pentamerus oblongus_, etc. (p. 468). Lower Llandovery slates (p. 469). Foreign Niagara limestone, with _Calymene, Homalonotus_, etc. (p. 479). Clinton group of America, with _Pentamerus oblongus_, etc. (p. 479). Silurian strata of Russia, with _Pentamerus_ (p. 477). 26. LOWER SILURIAN. British Bala and Caradoc beds (p. 470). Llandeilo flags (p. 473). Arenig or Stiper-stones group (Lower Llandeilo of Murchison) (p. 475). Foreign Ungulite or Obolus grit of Russia (p. 477). Trenton limestone, and other Lower Silurian groups of North America (p. 479). Lower Silurian of Sweden (p. 477). CAMBRIAN 27. UPPER CAMBRIAN. British Tremadoc slates (p. 483). Lingula flags, with _Lingula Davisii_ (p. 484). Foreign “Primordial” zone of Bohemia in part, with trilobites of the genera _Paradoxides_, etc. (p. 487). Alum schists of Sweden and Norway (p. 489). Potsdam sandstone, with _Dikelocephalus_ and _Obolella_ (p. 489). 28. LOWER CAMBRIAN. British Menevian beds of Wales, with _Paradoxides Davidis_, etc. (p. 484). Longmynd group, comprising the Harlech grits and Llanberis slates (p. 485). Foreign Lower portion of Barrande’s “Primordial” zone in Bohemia (p. 486). Fucoid sandstones of Sweden (p. 489). Huronian series of Canada? (p. 490). LAURENTIAN 29. UPPER LAURENTIAN. British Fundamental gneiss of the Hebrides? (p. 493). Hypersthene rocks of Skye? (p. 491). Foreign Labradorite series north of the river St. Lawrence in Canada (p. 491). Adirondack mountains of New York (p. 491). 30. LOWER LAURENTIAN. British Wanting? Foreign Beds of gneiss and quartzite, with interstratified limestones, in one of which, 1000 feet thick, occurs a foraminifer, _Eozoon Canadense_, the oldest known fossil (p. 491). CHAPTER IX. CLASSIFICATION OF TERTIARY FORMATIONS. Order of Succession of Sedimentary Formations. — Frequent Unconformability of Strata. — Imperfection of the Record. — Defectiveness of the Monuments greater in Proportion to their Antiquity. — Reasons for studying the newer Groups first. — Nomenclature of Formations. — Detached Tertiary Formations scattered over Europe. — Value of the Shell-bearing Mollusca in Classification. — Classification of Tertiary Strata. — Eocene, Miocene, and Pliocene Terms explained. By reference to the tables given at the end of the last chapter the reader will see that when the fossiliferous rocks are arranged chronologically, we have first to consider the Post-tertiary and then the Tertiary or Cainozoic formations, and afterwards to pass on to those of older date. Fig. 86: Order of Superposition of Deposits