SYNOPSIS OF CONTENTS. INTRODUCTION. PART I.— LOWER PALAEOZOIC STRATA. Chapter I.—Stratigraphical or Historical Geology—the History of the Formation of the Earth’s Crust. PAGE Geological time, divisions of . 3 The progress of life, subdivisions based upon .... 4 The seven ages .... 4 PAGE Periods and epochs, subdivisions into ...... 6 The known fossiliferous strata . 8-14 Palaeozoic rocks of North America 15 Thickness of stratified rocks . 15 Chapter II.—Pre-Cambrian Period. Archaean or Azoic rocks Dana’s four eras .... Texture of Archaean rocks . Distribution of „ . . The Huronian rocks of America and Europe, comparison of 16 Results of inquiries into the origin 17 of the Archaean rocks . . 21 17 First appearance of life . . 22 18 Probable conditions under which the Cambrian and Silurian rocks 20 were deposited in Europe . 24 Conclusions and deductions . 25 Chapter III.—The most Ancient Stratified British Rocks. The ten most ancient areas— (I.) Anglesea. ... 26 (2.) Bangor and Llanberis . 26 (3.) The Lleyn promontory . 26 (4.) The Harlech district . 27 (5.) St. David’s ... 27 (6.) Longmynd ... 27 (7.) Malvern .... 27 (8.) Ch am wood Forest . . 27 (9.) Wexford and Wicklow . 27 (io.) The Western Highlands of Scotland ... 28 Chapter IV.—Lower CAMBRIAN Period. The Cambrian system ... 28 The Cambrian system as defined by Sedgwick .... 29 Longmynd, Llanberis, and Har ¬ lech groups .... 29 St. David’s section ... 30 Irish Cambrian rocks . . . 32 ' Dr. Hicks’ grouping of Lower Cambrian rocks 33 Chapter V.—Paleontology of the Lowest Cambrian Rocks. The Lower Cambrian areas con- Harlech and Longmynd fauna . 36 trasted 35 Palaeontological summary . . 40