34^ SILURIAN DISTRICT OF RHYMNEY AND PEN-Y-LAN. 



Devonian seas. The sandstones with Old-Red characters, such as 

 the Hangman Grit and the Pickwell-Down Sandstones, occurring 

 in the Devonian formation were deposited at intervals when this 

 barrier was submerged to a greater depth than usual. The 

 Cornstones were stated to thin out to the south, along with the 

 other sedimentary beds of the Old Red Sandstone, and were 

 regarded as derived from the denudation of previously upheaved 

 limestones such as the Bala and Hirnant. The paper concluded 

 with a description of the more interesting rocks and fossils. 



