Devonian Era in the Ohio Basin. — Clay pole. 29 
common, such as Cyathophyllum caespitosnin and Pleurodict- 
yon problematicum, is satisfactory evidence that, though com- 
munication was less free, it was not altogether broken up. 
When we find well known Appalachian corals such as Zaph- 
rcntis gigantea and other fossils, as Spirifcra gregaria, in the 
Gaspe region, it is equally clear that there was continuous sea 
between these areas. 
In the Corniferous period then an open sea extended from 
an unknown shore in the far west across the Mississippi val- 
ley to an eastern Atlantic margin approximately laid down 
on our map. Its southern limit in the western portion cannot 
be easily marked. A long and wide channel ran to the north- 
east, along a great part of which Corniferous traces have been 
effaced, but where enough still remains to indicate the past 
existence of wider deposits. In the far northeast however the 
beds ceased to be calcareous to the same extent and they be- 
tray somewhat more signs of a shore. 
, Indirect inference enables us to sharpen up this picture and 
fill in a few more details. Over almost all this immense area 
the Corniferous limestone maintains a yery uniform thickness 
and composition. Except in a' few spots, it seldom exceeds 
one hundred feet and consists of a very pure limestone ming- 
led in most of its exposures with a greater or less quantity of 
chert. It is therefore safe to infer that during its deposition 
no important change of level occurred in the sea- bottom and 
that no great upheaval elevated the bordering lands of Ap- 
palachia. However long the period may have been it was a 
time of repose in Ohio and the adjoining states. Century 
after century and millennium after millennium the calcareous 
sediment sank and slowly built up the massive limestone beds, 
entombing within it myriads of relics of contemporaneous life. 
Xot only were there no violent catastrophes and no volcanic 
eruptions to break the Corniferous peace within the Ohio area, 
but no secular and gentle oscillations, which have so strongly 
characterized the Appalachian area, were in progress when 
the period began nor during its long continuance. Further- 
more, the Corniferous sea was one of clear, bright water un- 
stained with mud and dirt and we may be warranted in the 
belief that it was not deep, perhaps fifteen to twenty fathoms. 
Equally safe is the inference that the temperature of this sea 
