THE GEOLOGY OF TYTHERINGTON AND GROVESEND. 17 



fications in topographical details, introduced from the six- 

 inch Survey map. When Mr. Sanders' map was printed, the 

 Tytherington cutting had not been made ; and the know- 

 ledge it gives us necessitates some changes in the boundaries 

 of the strata. 



(1) Carboniferous rocks (Upper Transition Beds) are proved 

 in the field to the east of the Station, where Mr. Sanders 

 marks Trias. I have therefore joined up the isolated patch 

 of Carboniferous, which Mr. Sanders shows to the west of 

 the Station, with the main mass of Tytherington Hill. 



(2) The patch of Trias proved by the section to exist 

 beyond the Tytherington Tunnel has been introduced, and 

 has been connected provisionally with the Trias inlet to the 

 west of Castle Hill. The contour of the ground seems to 

 me to justify this. 



(3) The outcrop of the Lower Transition Beds is proved by 

 the section to lie, near Grrovesend, somewhat further to the 

 south than is indicated by Mr. Sanders ; and the boundary 

 of the Old Bed Sandstone must also be be brought some 

 distance further down in the same direction. 



These modifications of the geological map will be clearly 

 evident, if that which is published with this paper be com- 

 pared with Sheet 4 of Mr. Sanders' admirable publication. 



Since the foregoing was in type, I have found the Bryozoa Bed in the 

 Mendips, in one of the lateral valleys of Burrington Combe. In Bur- 

 lington Combe the Gully Oolite is also well represented. 



