168 The American GeologUt. September, i892 
Tennessee and Alabama. It was as early as the age of the Oris- 
kany that the separation of the typical southern from the typical 
northern faunas took place, and in the extreme northeastern ex- 
tension of the Appalachian region, the Acadian province of Maine 
and New Brunswick, we observe that this is the highest marine 
fauna reached in the Devonian. 
Elevation evidently shut out access to the sea for this region. 
It is from that time on that the faunas of the Appalachian region 
present their essential relation to the southern hemisphere faunas, 
and show the absence of the typical European fauna. We assume, 
therefore, that a barrier was raised that shut off connection with 
European regions during the lower Devonian. The elevation to 
the south took place somewhere near the close of the Hamilton, 
and the theory we propose is that an elevation such as to divert 
the currents, bringing in first the Cuboides fauna from the north- 
west and finally replacing entirely the Hamilton by the Chemung 
as far east as New York is the reasonable explanation of the 
facts. 
The interesting point is that the testimony of the migrating 
fauna chronologically agrees with the testimony of the oscillation, 
as recorded in the deposits. 
All along the southern limits of Devonian exposures in the 
United States there is indication of an oscillation upward and then 
downward between the Hamilton and the beginning of the Car- 
boniferous. 
The succession of faunas in New York indicates a change at 
the close of the Hamilton from a fauna whose closest affinities 
we're with the South American faunas, to a fauna whose earlier 
stages were seen in Iowa, Nevada and the Mackenzie river, and 
whose affinities were with the Asiatic and European Devonian. 
In Arkansas and Tennessee the faunas of the Black Shale indi- 
cate that the first marine fauna to appear after the elevation and 
erosion are of an age as late as the Cleveland shale of Ohio, /. e., 
the very terminal parts of the Devonian or beginning of the Car- 
boniferous. This event, it will be noticed, is associated with 
that general elevation of the continent, beginning in the northeast, 
which is expressed by the cessation of marine faunas, and ter- 
minating in the Coal Measures and the final elevation above the 
surface of the great mass of the continent east of the Mississippi 
river. 
