Devonian System.

Devonian System. The name proposed by Murchison and Sedgwick to replace the more characteristic and older term Old Red Sandstone, because the slaty and calciferous strata in Devonshire contain a much more copious and rich fossil fauna than the red arenaceous rocks of Scotland, Wales, and Herefordshire, with which they are believed to be upon the whole contemporaneous. The physical condition under which the strata in Devonshire were deposited differed greatly from those which marked the accumulation of the Old Red Sandstone, and there is still some doubt as to the precise correlation of the two sets of strata. Geologists, therefore, retain both names, and speak of the Devonian and Old Red Sandstone system, or Old Red Sandstone and Devonian system. See OLD RED SANDSTONE.