DEVONIAN AND OLD RED PERIOD. 135 



Red Sandstone" was originally applied, to distinguish them 

 from certain arenaceous strata which lie above the coal (" New 

 Red Sandstone"). The Old Red Sandstone, properly so- 

 called, was originally described and investigated as occurring 

 in Scotland and in South Wales and its borders; and similar 

 strata occur in the south of Ireland. Subsequently it was 

 discovered that Sediments of a different mineral nature, and 

 containing different organic remains, intervened between the 

 Silurian and the Carboniferous rocks on the continent of Eu- 

 rope, and strata with similar palaeontological characters to these 

 were found occupying a considerable area in Devonshire. The 

 name of " Devonian " was applied to these deposits ; and this 

 title, by common usage, has come to be regarded as synony- 

 mous with the name of " Old Red Sandstone. " Lastly, a 

 magnificent series of deposits, containing marine fossils, and 

 undoubtedly equivalent to the true " Devonian " of Devon- 

 shire, Rhenish Prussia, Belgium, and France, is found to inter- 

 vene in North America between the summit of the Silurian 

 and the base of the Carboniferous rocks. 



Much difficulty has been felt in correlating the true " Devon- 

 ian Rocks" with the typical "Old Red Sandstone" this diffi- 

 culty arising from the fact that though both formations are 

 fossiliferous, the peculiar fossils of each have only been rarely 

 and partially found associated together. The characteristic 

 crustaceans and many of the characteristic fishes of the Old 

 Red are wanting in the Devonian; whilst the corals and 

 marine shells of the latter do not occur in the former. It is 

 impossible here to enter into any discussion as to the merits 

 of the controversy to which this difficulty has given origin. 

 No one, however, can doubt the importance and reality of the 

 Devonian series as an independent system of rocks to be in- 

 tercalated in point of time between the Silurian and the Car- 

 boniferous. The want of agreement, both lithologically and 

 palseontologically, between the Devonian and the Old Red, 

 can be explained by supposing that these two formations, 

 though wholly or in great part contemporaneous, and therefore 

 strict equivalents, represent deposits in two different geograph- 

 ical areas, laid down under different conditions. On this view, 

 the typical Devonian rocks of Europe, Britain, and North 

 America are the deep-sea deposits of the Devonian period, or, 

 at any rate, are genuine marine sediments formed far from 

 land. On the other hand, the " Old Red Sandstone " of 

 Britain and the corresponding " Gaspe Group " of Eastern 



