OLD RED SANDSTONE AND DEVONIAN PERIOD. 93 



circumstance that the 5 beds exposed give 



: shallow-? ;onditions in con- 



en in North Devon 

 >et, in the beds known as the 

 1 and Linton group. In South DeVon 

 the lowest purple slaty rocks. The 



mid ^"<>up, though mainly 



tains a little limestone. 



Us* 



CARUONin ROUS 



\V. E, 



in from •' ; how the Silurian, 



Old k-<i - . and Carl folded be- 



:iirc 



ne becomes more abundant in South 

 Plymouth ai ften taking 



metimes 

 thinning off into the shales. The uppermost 

 Devonian known as the Pilton group in North 

 Devon - sandstone. In Cornwall ti. 



rocks are n by limestones and slates at 



lerwyn. 



triking feature of these rocks is the 

 remarkable change which takes place in the 

 marine life. The multitude of genera which had 

 survived more or mspicuously from the 



Cambrian to the Silurian time becomes replaced 

 by new sets of types which are substantially the 

 same as survive through the marine beds of the 



