112 =J. 8S. Newberry on the so-callea Land Plants of Ohio. 
universally of mere casts of their external surface, carbonaceous 
matter and internal structure having both entirely disappeared. 
The physical condition of the region about Cincinnati, during 
the Lower Silurian age, strengthens the conclusion that the spe- 
cimens under consideration are not the remains of land plants. 
As I have shown elsewhere,* the Cincinnati arch was raised at 
the close of the Lower Silurian age. Subsequent to that time 
it formed a group of islands, which, during the Devonian age, 
were probably covered with a luxuriant terrestrial vegetation. 
But during the period when the Cincinnati group was deposited 
an open sea occupied all this part of the Mississippi Valley. 
The shores of this sea were formed by the Blue Ridge, the 
discovered in the Lower Cambrian sandstones of Sweden, and 
two Paper of these have been described (Hophyton Linneanum 
, and #. Torelli Linnarsson). The specimens are sai 
algologists not to be the remains of alge, but they are consid- 
ered to be vascular cryptogams or monocotyledons. It is not 
certain, however, that they are not thallogens, as all traces of 
structure are lost and nothing is left but the impression of the 
external surface.+ 
e evidence of the existence of land plants during the Upper 
_— age is more satisfactory. Prof. J. W. Dawson of 
ontreal has announced the discovery of vascular cryptogams 
* Geological Survey of Ohio, vol. i, part i, page 93. 
+ Geological Magazine, Sept., 1869. [In the Ofversigt af Kongl. Vetenskaps- 
Akademiens Forhandlingar, = 9, —_ (the Bulletin of the Royal 
“ an 
several plates, 18 
