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CONTENTS. 



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INTRODUCTION v 



CHAPTER I. THE ELEMENTS OF A PALEOGEOGRAPHIC PROBLEM i 



A. The nature of the problem 2 



B. Outline of points to be considered in any paleogeographic problem 2 



I. Stratigraphic limits of the unit to be considered 2 



(a) Isolation of the unit by the nature of the deposits 3 



Marine deposits 3 



Coastal deposits 3 



Shallow-water deposits 5 



Deep-water and abyssal deposits 5 



Cut-off arms of the sea 6 



Xon-marine saline deposits 6 



Brackish-water deposits 7 



Fresh-water deposits 8 



Subaerial deposits (fluviatile, delta, and aeolian) 8 



Glacial deposits II 



Metamorphosed sediments 12 



Igneous rocks 12 



(6) Isolation of unit by limiting planes 12 



II. Geographical limits of the unit 14 



(a) Mapping of the limits 14 



(b) Location of source of material 14 



(c) Seaward limits of the unit 15 



(d) Lateral changes in the beds 16 



(e) Positive and negative areas 16 



III. Interpretation of the adjacent lands 17 



(a) Direct contact of observed surfaces of degradation 17 



(6) Physical character of deposits 17 



(c) Mineral content 18 



(d) Fossil content 19 



IV. The fossil content of the unit 19 



(a) The fauna of the unit 19 



(6) Origin of the fauna 20 



Aquatic invertebrate fauna 2O 



Terrestrial invertebrate fauna 23 



Terrestrial vertebrate fauna 23 



(c) Character of the fauna 24 



(d) Phylogenetic relations of the fauna 24 



(e) Peculiarities of the fauna 25 



(f) Radiation and depression of life 26 



(g) The interrelations of the fauna 27 



(h) Faunal elements as time markers 29 



(*) The flora of the unit 29 



V. Correlation of unit with other beds 32 



\'l. Climatology of the past 33 



VII. Distribution of the fauna and flora 34 



(a) Provincial or cosmopolitan 34 



(6) Distribution dependent upon the character of the biota 34 



(c) Distribution dependent on the inorganic environment 35 



(d) Migration 36 



(e) Autochthony 37 



(/) Accidental introduction 37 



(g) Extinction of a fauna or flora 38 



(h) Survivals and precipitate development 38 



(i) Control of distribution 39 



(j) Environment 40 



VIII. Checks on the geologist 42 



IX. Checks on the biologist 43 



(a) Bridges and barriers 43 



iii 



