104 Royal Society. 
The term “ Erian ” is applied to the formations included between 
the top of the Upper Silurian and the base of the Carboniferous, on 
limitation of the Devonian of Europe, and also on account of the 
immense area occupied by these beds on the south and west of Lake 
Erie, and their gear development wit th regard to subdivisions 
and fossils. The name “Erie Division” was also that Mp pen 
Lower Devonian, were described, and full details given of the form, 
structure, and fructification of two species of Psilophyton. The 
eg 
were examined and corrected, and several interesting trunks and stipes 
belonging to Tree-ferns were described. The fruits of the genus 
Cardiocarpum were illustrated with reference to their structure. 
he occurrence of Lepidophloios, ine EA and other forms in 
the Middle Devonian was noticed for the first 
The third part of the memoir was tuii h comparisons and 
general conclusions. At the close of the Upper Silurian period there 
was a great subsidence of the land in Eastern America, proved b 
the wide extent of the marine beds of the Lower Helderberg (Lud- 
low) group. It was on the small areas of Lower-Silurian and Lau- 
Devo 
extension in the shallow-water beds of the Lower Erian. The 
subsidence inditéted by the great Corniferous limestone interrupted 
these conditions on the west side of the Appalachians, but not on 
their eastern side. At the close of eee e find the rich Middle- 
ppalachians terminated the Erian age, it is followed by the bm 
and quite dissimilar flora of the Lower Carboniferous ; and this, after 
the subsidence indicated by the Carboniferous limestone, is followed 
by the Coal-formation flora. 
If we compare the Erian and Carboniferous floras, we find that 
the ene oe of the latter are represented in the former (but, 
st part, under distinct specific forms), that the Erian 
erous. 
In comparing the Erian flora of America with the Devonian of 
ST E 
