TRANSACTIONS OF SECTION C. 603 



also fiud fragments of that zone at the foot of the reef in the breccia, we should 

 have excellent data for determining the actual depth of the carboniferous sea at that 

 particular point. 



Postscript. — In speaking of the mounds as ' knoll-reefs' I do not wish necessarily 

 to imply that they were Coral-reefs. Tliey seem to have lu-on built up in a some- 

 what siiuihir way, but corals apparently only played a subordinate part in their 

 formation. 



