414 PROCEEDINGS OV THE GEOLOGICAL SOCIETY. [DeC. 1, 



transverse division whatever, and could not, therefore, I presume, 

 he referred to Calamites. They are unKke any Carhoniferous plant 

 ever discovered, and on that account also are, in all prohahilitj, to 

 he grouped with the plant-hearing Upper Devonian beds of Saalfeld 

 in Germany and other places. 



General View of the Old Red or Devonian Rocks *. — The method 

 of grouping the Old Red Sandstone deposits of Caithness, the Ork- 

 neys, and the north-eastern counties of Scotland, as above described, 

 is in accordance with the tripartite division of their geological equi- 

 valents, the Devonian rocks of Devonshire, Belgium, and Germany. 

 Eef erring to the Table of Classification published in ^ Siluria,' I 

 would here also indicate how unanswerably the zoological contents 

 of the Devonian rocks of Russia (i. e. of deposits lying clearly be- 

 tween the uppermost Silurian and the lowest Carboniferous stratum) 

 sustain my belief that the Old Eed of Scotland and Herefordshire 

 is the equivalent of this intermediate group on the continent of 

 Europe. Proofs of the intermingling, in the same beds, of the sea- 

 shells of the Devonshire hmestones, with species of fishes identical 

 with those of the Scottish Old Red Sandstone (the identity being 

 determined by Agassiz), were first given in the work * Russia and the 

 Ural Mountains,' and were, I then presumed (1845), sufficient to de- 

 monstrate the truth of my inferences. Perceiving, however, that 

 scepticism still partially prevailed on this subject, and that, Russia 

 being far off, the statement of my associates and self had not made 

 such an impression as the facts called for, I wrote to my friend Colonel 

 Helmersen, who has given much attention to the stratigraphical ar- 

 rangement and zoological contents of the Devonian rocks of Russia, 

 and, referring to the recent admirable publication of Pander, I re- 

 quested him to inform me distinctly to what extent the ichthyoHtes 

 of the Old Red Sandstone of Scotland were commingled in Russia 

 with Devonian mollusks. His answer was clear and decisive, in 

 assuring me that there are many places, besides those seen by my 

 associates and self, where the marine mollusca of Devon and the Bou- 

 lonnais are mixed up with Scottish species of Old Red ichthyoHtes. 



The lowest known Devonian strata in the north of Livonia, and 

 thence ranging into the Government of St. Petersburg, repose trans- 

 gressively upon various members of the Silurian rocks. Thus, in 

 the Isle of Oesel, as described in a memoir recently read before this 

 Society t, the uppermost Silurian rocks of the Isle of Oesel are 

 shown, from the shells they contain, to be perfect representatives 

 of the Ludlow rocks of England. With these are associated portions 

 of many new genera, in addition to the Onchus and Thelodus of those 

 British Upper Ludlow rocks ; and with them two new species of the 

 Cephalasjpis have also been shown to occur. Thus far the physical 

 and zoological relations of the uppermost Silurian rocks of Russia 

 are in accordance vnth those of the typical region of England. 

 Whilst, however, the latter affords evidence of a complete and un- 

 broken transition upwards into the overlying Old Red, the same 



* See Tables at pp. 437-439. t Quart. Journ. GTeol. See. vol. xiv. p. 48. 



