CHAP. V.] DEVONIAN PEEIOD. 59 



2. Geographical Restoration. 



During this period great geographical changes took 

 place ; the greater part of Britain was elevated into dry 

 land, and formed part of a continent which must have had 

 a considerable extention to the north and west of our 

 islands. The sea which covered so large a part of the 

 British area in Silurian times was now contracted into a 

 much smaller space, and only lay over the southern part of 

 England, whence it stretched eastward through the north of 

 France and Belgium. Westward it seems to have extended 

 into Ireland (if the Glengariff grits are marine beds), but 

 can only have covered a comparatively small area in the 

 extreme south-western part of the country. 



An arm of the sea is represented on the map (PI. II.) as 

 covering the area occupied by the Old Eed Sandstone of 

 Wales and Shropshire, for Professor Hull's opinion that 

 this was formed in a bay or estuary which opened out of 

 the Devonian sea seems more probable than the view 

 advocated by Sir A. Ramsay and Dr. Geikie, who regard it 

 as a purely lacustrine deposit. 



Sir A. Ramsay points to the prevalent red colour of the 

 rocks, but red rocks can be formed in seas as well as 

 lakes. The organic remains are few ; there are fish and 

 large Crustacea, such as occur in the Scottish Old Red 

 Sandstone, but these may have been able to exist both in 

 salt and fresh water, like many fish at the present day. 

 The marine shell Lingida cornea, is said to occur in some 

 of the Cornstone beds, and this would certainly prove the 

 beds containing it to have been formed in salt water. 

 Lastly, we may observe that there is no physical evidence 

 to support the supposition of a land barrier to the south. 



At the same time it is true that the Cornstone and Tile- 

 stone series hardly present the usual characteristics of an 

 estuarine deposit, and the inlet may have been a long bay 



