remains of those two members of the series which are known as the “Old Red Sandstone” and the “Devonian” rocks proper.  This discrepancy, however, is not complete; and, as we have seen, can be readily explained on the supposition that the one group of rocks presents us with the shallow water and littoral deposits of the period, while in the other we are introduced to the deep-sea accumulations of the same period.  Nor can the problem at issue be solved by an appeal to the phenomena of the British area alone, be the testimony of these what it may.  As a matter of fact, there is at present no sufficient ground for believing that there is any irreconcilable discordance between the succession of rocks and of life in Britain during the period which elapsed between the deposition of the Upper Ludlow and the formation of the Carboniferous Limestone, and the order of the same phenomena during the same period in other regions.  Some of the Devonian types of life, as is the case with all great formations, have descended unchanged from older types; others pass upwards unchanged to the succeeding period:  but the fauna and flora of the Devonian period are, as a whole, quite distinct from those of the preceding Silurian or the succeeding Carboniferous; and they correspond to an equally distinct rock-system, which in point of time holds an intermediate position between the two great groups just mentioned.  As before remarked, this conclusion may be regarded as sufficiently proved even by the phenomena of the British area; but it maybe said to be rendered a certainty by the study of the Devonian deposits of the continent of Europe—­or, still more, by the investigation of the vast, for the most part uninterrupted and continuous series of sediments which commenced to be laid down in North America at the beginning of the Upper Silurian, and did not cease till, at any rate, the close of the Carboniferous.

LITERATURE.

The following list comprises the more important works and memoirs to which the student of Devonian rocks and fossils may refer:—­

 (1) ‘Siluria.’  Sir Roderick Murchison.
 (2) ‘Geology of Russia in Europe.’  Murchison (together with De
     Verneuil and Count von Keyserling).
 (3) “Classification of the Older Rocks of Devon and Cornwall”—­’Proc. 
     Geol.  Soc.,’ vol. iii., 1839.  Sedgwick and Murchison.
 (4) “On the Physical Structure of Devonshire;” and on the
     “Classification of the Older Stratified Rocks of Devonshire
     and Cornwall”—­’Trans.  Geol.  Soc.,’ vol. v., 1840.  Sedgwick
     and Murchison.
 (5) “On the Distribution and Classification of the Older or Palaeozoic
     Rocks of North Germany and Belgium”—­’Geol.  Trans.,’ 2d ser.,
     vol. vi., 1842.  Sedgwick and Murchison.
 (6) ‘Report on the Geology of Cornwall, Devon, and West Somerset.’ 
     De la Beche.
 (7) ‘Memoirs of the Geological Survey