35 



DEVONIAN ERA. FISHES ABUNDANT. 



WE now advance to a new chapter in this marvellous history 

 that of the Devonian era. The term Devonian System is 

 applied to an important and conspicuous group of strata, 

 overlying the Silurian, and largely developed first in the 

 South of Devonshire (whence the name), and in Cornwall, 

 South Wales, Herefordshire, Shropshire, and Worcestershire ; 

 also in Scotland, the valley of the Rhine, Russia, and the west- 

 ern states of America ; besides, in all probability, many parts of 

 the world as yet unexplored. In Scotland, the great Gram- 

 pian elevation, composed of granite and gneissic rock, is 

 skirted by a dense formation of conglomerate and red sand- 

 stone, extending in a sweep from Dunbarton to Stonehaven, 

 and so on to Morayshire, Ross, and Caithness. This passes 

 by the general name of the Old Red Sandstone, which was at 

 first used as an appellative for the system ; but it has latterly 

 been abandoned, as redness is not found to be a prevailing 

 peculiarity of the strata in other countries. In Russia, a 

 surface as large as the whole of Great Britain is occupied by 

 this formation. It reaches a thickness of ten thousand feet 

 in England. 



The general forms of life prevalent in the Silurian era are 

 continued in the Devonian, with the remarkable addition of a 

 large development of the humblest vertebrate class Fishes. 

 There is here, as there was in the Silurians, an abundance of 

 zoophytes, corallines, crinoids, crustaceans, and mollusks, 

 but mostly presenting those inferior variations which natural- 

 ists regard as constituting distinct species : speaking strictly, 

 D2 



