A CIRCUM-INSULAR PALAZOZOIC FAUNA. 
CONTENTS. 
Introduction. 
Zoological Provinces of Devonian Time. 
Distribution of Land and Water during Devonian Time. 
Union of Eastern and Western Devonian Provinces. 
Generic Evidence of the Origin of the Littoral Fauna about the Ozark Island. 
Specific Evidence of the Origin of the Littoral Fauna about the Ozark Island. 
Conclusion. 
INTRODUCTION. 
Zoodlogists who have turned their attention to the geographic 
distribution of animal life on the earth at the present time, have 
divided it into numerous zodlogical provinces. The marine 
zo6logical provinces are separated by three classes of barriers, 
(oy Climaticw(2) and (3) sbyssmaley Maach) one otmthese 
establishes a limit to the migrations of marine life. There is no 
reason to doubt the existence of zodlogical provinces in past 
time similar to those existing today, with the same sorts of bar- 
riers, but ever changing with the progress of time. 
These zodlogical provinces of past time give rise to problems 
with which the paleontologic geologist has to deal. Unfor- 
tunately the ancient barriers are obscured or lost, being buried 
by later formations, or the sea, or carried away by erosion, and 
it falls to the investigator to reconstruct the barriers from a study 
of the faunas and of the stratigraphy. 
Zovlogical provinces of Devonian time.— During Silurian time 
the faunas of eastern North America and northern Europe were 
intimately related. Many species were common to both regions, 
and there seems to have been freedom for intermigration between 
the two. With the beginning of Devonian time these two regions 
became isolated. The faunas in each continued their evolution, 
but each in accordance with the conditions of its own environ- 
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