TABLE OF CONTENTS xxxi 



PAGE 



Petrifaction of Mineral Structures (1082); a. Protozoa 

 (1082); b. Sponges and Hydrozoans (1082); c. Silicifica- 

 tion of Corals (1083); d. The Brachiopod Shell (1083); 

 e. Shells of Molluscs (1084); f. Crustaceans Merostomes, 

 Insects, etc. (1086); g. Echinoderms (1086); h. Verte- 

 brates (1088) 1082-1088 



Excessive silicification 1089 



Molds and Casts 1089 



2. Tracks, Trails and Burrows of Animals 1090 



3. Artificial Structures 1093 



4. Coprolites 1093 



Mechanical Deformation of Fossils 1094 



Index Fossils 1094 



Bibliography XXX 1095 



G. PRINCIPLES OF CLASSIFICATION AND CORRELATION OF 

 GEOLOGICAL FORMATIONS. 



CHAPTER XXXI. 



Nomenclature and Classification of Geologic Formations 1097 



Development of Classifications 1097 



Selection of the Type Section 1 100 



Time Scale and Formation Scale 1 102 



Subdivision of Time and Formation Scales (1103); I. Inter- 

 national Geological Congress (1104); II. Dana's System 



(1106); III. United States Geological Survey 1103-1106 



Unification of Terminology (i 107) ; Local Stages and Substages 1 107 

 Principles Governing the Naming of Formations (1109); Selection 



of Names for Systems, Series and Stages (Groups) 11 09-1 1 1 1 



Mapping (11 12); Mapping on Formational Basis (11 12); Mapping 

 on Faunal Basis (11 13); Mapping of Discontinuous Formations 



(II 13) 1112-1113 



Types of Geological Maps (11 15); Formation and System 

 Maps (11 15); Intermediate Maps (11 15); Notation of Forma- 

 tions on Map (11 16); Legend (1116) 1115-11 16 



Continuous and Discontinuous Mapping 11 1 7 



Sections; Types of Sections 1117 



The Length of Geological Time 1118 



Bibliography XXXI 1 1 19 



CHAPTER XXXIL 



Correlation, Its Criteria and Principles. Pal/eogeography 1121 



Correlation 1121 



History of Development of Methods of Correlation 1 121 



Chronological Equivalency; Contemporaneous and Homo- 

 taxial Formations (i 124); Contemporaneity of Faunas 



(1125); Prenuncial Faunas; Colonies 1124-1126 



Standard or Type Section (i 127) ; A Double Standard . 1 127-1 129 



