CLASSIFICATION. 
439 
CHAPTER XXV. 
D'EYOmAN OR OLD RED SANDSTONE GROUP. 
Classification of the Old Red Sandstone in Scotland and in Devonshire.— 
Upper Old Red Sandstone in Scotland, with Fish and Plants.—Middle 
Old Red Sandstone.—Classification of the Ichthyelites of the Old Red, 
and their Relation to Living Types.—Lower Old Red Sandstone, with 
Cephalaspis and Pterygotus. —Marine or Devonian Type of Old Red Sand¬ 
stone.—Table of Devonian Series.—Upper Devonian Rocks and Fossils. 
—Middle.—Lower.—Eifel Limestone of Germany.—Devonian of Russia. 
—Devonian Strata of the United States and Canada.—Devonian Plants 
and Insects of Canada. 
Classification of the two Types of Old Red Sandstone.— We 
have seen that the Carboniferous strata are surmounted by 
the Permian and Trias, both originally included in England 
under the name “Xew Red Sandstone,” from the prevailing 
red color of the strata. Under the coal came other red 
sandstones and shales which were distinguished by the title 
of “Old Red Sandstone.” Afterwards the name of “Devo¬ 
nian ” was given by Sir R. Murchison and Professor Sedg¬ 
wick to marine fossiliferous strata which, in the south of 
England, occupy a similar position between the overlying 
coal and the underlying Silurian formations. 
It may be truly said that in the British Isles the rocks of 
this age present themselves in their mineral aspect, and even 
to some extent in their fossil contents, under two very differ¬ 
ent forms; the one as distinct from the other as are often 
lacustrine or fluviatile from marine strata. It has indeed 
been suggested that by far the greater part of the deposits 
belonging to what may be termed the Old Red Sandstone 
type are of fresh-water origin. The number of land-plants, 
the character of the fishes, and the fact that the only shell 
yet discovered belongs to the genus Anodonta^ must be al¬ 
lowed to lend no small countenance to this opinion. In this 
case the difficulty of classification when the strata of this 
type are compared in different regions, even where they are 
contiguous, may arise partly from their having been formed 
in distinct hydrographical basins, or in the neighborhood of 
the land in shallow parts of the sea into which large bodies 
of fresh water entered, and where no marine mollusca or cor¬ 
als could flourish. Under such geographical conditions the 
limited extent of some kinds of sediment, as well as the ab- 
