JAMES REID ON MARINE ORIGIN OF OLD RED SANDSTONE. 27 
P. hibernicus^ Psilophyton^ Lepidodendron^ ferns, and numerous tree 
ferns; some of which closely resemble Caidopteris Peachii of Caith¬ 
ness. The plants of the Old Red Sandstone of Scotland are, in a 
large measure, but poorly preserved. In illustration of the doubtful 
character of some of our Scottish plants, we may instance the case of 
Arthrostigma^ which, since 1877, had been doubtfully referred to 
Psilophyton and Arthrosdgma, till, in 1890, Sir J. W. Dawson recog¬ 
nised Arthrostigma gracile amongst some fossil plants from Perth¬ 
shire.* 
That traces of sea-weeds have been met with in the Old Red 
Sandstone of Scotland is a fact which can scarcely be doubted. 
Pachytheca occurs in the sandstones of Murthly, and in Forfarshire, 
and the late Professor Page has figured an undoubted fucoid from 
Roxburghshire, while Nicholson says, “the Old Red Sandstone of 
Scotland contains a good many fragments supposed to belong to 
sea-weeds.” f 
In Gaspe, Nematophyton, which has been referred by Professor 
Penhallow and Carruthers to the algce^ has been numerously met 
with. 
MARINE SHELLS OF THE OLD RED SANDSTONE. 
The singular fact that no marine shells occur in the red sandstones 
and marls of the Russian Devonian, although these contain Old Red 
Sandstone fishes, throws light upon the general absence of similar 
fossil remains in the red sandstones and shales of the Old Red 
Sandstone of Britain. Yet traces of the occasional presence of 
mollusks have been met with. Serpula and Conularia occur in the 
Welsh area, and Orthoceras dimidiatum (of the passage beds of 
England), Spirorbis, and other fossil remains, have been found in 
Lanarkshire. 
The Silurian genera of Eurypterids and Placoderms, which occur 
in the Old Red Sandstone of Lanarkshire and Ayrshire in the west, 
and Bridge of Allan, E. Berwick, and Forfarshire in the east of 
Scotland, undoubtedly point to the presence of a Devonian sea which 
spread continuously from one side of Scotland to the other. The 
limestone deposits of Nova Scotia have been referred to by Sir J. W. 
Dawson, as follows :—“ In other words, they belong to groups of the 
same age as the Devonian of England and the Old Red Sandstone 
of Scotland. . . . With respect to the fossils, I may remark that 
they are all marine; that they belong to numerous genera and 
species.” J 
“ Some of the fine beds (Gaspe) hold shells of Linguta and 
Modiomorpha of Hall.” § 
* Nature. Apr. 10, 1890. Page 537. Manual of Palceontology, 1872. Page 521. 
X Acadian Geology. 1855. Page 315. 
§ Report Geological Survey of Canada. 1871. Page 9. 
