STUDIES FOR STUDENTS. 
GEOLOGIC STUDY OF MIGRATION OF MARINE 
JON WIBIR IM SANIT ISS), 
CONTENTS. 
Introduction. 
Zoological Provinces. 
Modern Provinces. 
Ancient Provinces. 
Migration. 
Causes. 
Extinction of faunas. 
Means. 
Barriers. 
Land barriers. 
Climatic zones. 
Water barriers. 
Criteria. 
Sporadic occurrence. 
Heterochronous appearance. 
Heterochthonous faunas. 
Conclusion. 
INTRODUCTION. 
THE migration of invertebrates is necessarily too slow to be 
observed in a few years, and only many successive generations of 
observers could throw light on it. While the present habits of 
these animals may be studied and inferences drawn as to their 
history, these inferences are probably often incorrect. The com- 
mon inference that fossil corals indicate a warm sea is an exam- 
ple; by this method the existence of a tropical sea in the Arctic 
regions during Palzozoic time has been inferred, and therefore 
great changes in physical geography. But it is well known that 
the elephant and the rhinoceros, which we regard as typical trop- 
ical animals, lived in the Arctic regions of the northern 
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