28 The American Geologist. Julv - , '"' :; 
The geography of the Corniferous period is similar. Its 
great limestone slightly overlaps the edge of the Niagara in 
New York, is missing in middle Pennsylvania and only crops 
out again in Pickaway county, Ohio, after a disappearance of 
500 miles ; indicating a considerable contraction of the waters 
beyond their already narrow limits. At this time the whole 
southern bight had disappeared and the great Appalachian 
gulf of Alabama, Tennessee, Kentucky, West Virginia and 
Maryland, with other adjoining and smaller areas had shrunk 
within dimensions comparatively very restricted. 
The Corniferous Sea. — The annexed map may serve to 
bring out some points more distinctly than could verbal de- 
scription, thereby rendering criticism more definite and useful. 
There is no room for doubt that the greater part of Ohio 
and of northwestern Pennsylvania, with central New York, 
the Ontarian and Michigan peninsulas, lakes Erie and Mich- 
igan, formed part of the Corniferous sea. Possibly the west- 
ern side of the last mentioned lake must be excepted, but this 
is not certain. Illinois and western Indiana, with a small part 
of Kentucky, the Mississippi basin and large areas outside of 
it especially to the northward as far as the Arctic region, were 
also included. 
The wide channel running away to the northeastward must 
be considered as represented rather than mapped, inasmuch as 
the whole region has suffered so severe a crumpling and eros- 
ion that restoration of the original outline is rendered exceed- 
ingly difficult. Of the existence of such a channel in earlier 
days there can be no doubt. A small outlier of Lower Helder- 
berg strata, in place, occurs on St. Helen's isle, close to Mon- 
treal, and numerous other exposures carrying the characteristic 
Devonian fossils can be seen through New England and New 
Brunswick to Nova Scotia. It is impossible to read the lists 
of identical species given by Hall and Lyell without admitting 
that in the Silurian era there must have been a communication 
with the European area, and it is not easy to see how this can 
have been the case unless it was along the line of the wide 
channel indicated on our map. The lessened number of Cor- 
niferous species common to Europe and America signifies that 
the connection between the two areas, though still actual, was 
reduced or interrupted. The occurrence of several species in 
