88 



CHAPTER VII. 



UPPER SILURIAN SERIES. 



THE strati graphical order of the UPPER SILURIAN SERIES 

 is shown in the table p. 30. They were deposited 

 under the following circumstances : The Lower Silu- 

 rian rocks in large areas in the British Islands and 

 in some other areas, were upheaved, more or less con- 

 torted, and in many places suffered a great amount 

 of denudation before the deposition of the Upper 

 Silurian strata began, which, therefore, in various 

 districts lie quite unconformably upon them. In the 



FIG. 19. 



1. Cwradoc sandstone (Lower Silurian"). 



2. Upper Llandovery beds. 



3. Wenlock shale. 



4. Wenlock limestone. 



5. Upper Ludlow. 



6. Aymestry limestone. 



7. Upper Ludlow. 



8. Old Red Sandstone. 



typical district of Wenlock and Ludlow the arrange- 

 ment of the various subdivisions of these Upper Silurian 

 strata is as shown in figs. 19 and 22, the bands of lime- 

 stone generally forming bold terraces, that look north- 



