4 CONTENTS. 
Chapter III — Continued. Page. 
Chemung formation and its fauna ... 82 
Spirifer disjunctus fauna 83 
Recurrence of the Tropidoleptus fauna in the epoch of the Spirifer dis- 
junctus fauna . 89 
Marine fauna above Oneonta sandstone of eastern New York 92 
Chapter IV. — Shifting of faunas 97 
Evidence of shifting of faunas associated with deposition of Oneonta 
sandstone 97 
Principles involved in shifting of geological faunas 103 
Biological consequences of shifting of faunas 105 
Effect of shifting of faunas on classification of geological formations . . 108 
Black shale sediments 109 
Portage formation sediments 110 
Fossiliferous shaly sediments of Ithaca group 110 
Red sandstone sediments 110 
Faunal shifting and correlation 112 
Chapter V. — Equivalency as interpreted by geologists . 117 
Diversity of interpretation 117 
Correlation of Devonian formation of Ohio, western New York, and 
eastern New York 120 
Chapter VI. — The bionic value of fossils 124 
General statement 124 
The terms ' ' species, ' * ; ' race, ' ' and ' ' generation " . _ _ 127 
Order of magnitude of bionic units . .__.'. 128 
Revised definition of the terms ' ' fauna ' ' and ' • f aunule " ' 131 
The bionic time scale 132 
Bibliography 135 
Index 141 
I I, L U S T R A T I N. 
Plate I. Comparative chart of the Middle and Upper Devonian formations 
of Ohio, Pennsylvania,, and New York 120 
