486 H. HICKS ON THE REMAINS OE PLANTS FROM THE 



been already referred to in several papers read before this Society ; 

 and its geological position is therefore well known. ' In the Survey 

 maps and sections its horizon is given as immediately at the base 

 of the Denbigh-grit and Flag series. It is shown to be separated 

 from the .Bala or Caradoc beds by only a very thin band of shales, which 

 also contain plant-remains. In the published sections across this 

 neighbourhood approximate thicknesses of bet ween 4000 and 5000 feet 

 of beds belonging to the Denbighshire-grit and "Wenlock series are 

 shown to occur in direct superposition to the beds in which the plants 

 are found. None of the beds belonging to the Ludlow series are 

 mentioned as occurring in these sections, the highest given being 

 "Wenlock : hence, if the former were deposited in this area, they have 

 all been since removed by denudation. 



The geological horizon of the plant-yielding beds in relation to 

 typical sections in other areas is rather difficult to define, since 

 hitherto the Denbighshire-grit series has not been satisfactorily 

 correlated with any other group. In the Survey sections the true 

 Wenlock beds are made to come in at an horizon somewhere about 

 2000 feet above these beds, and to occupy the remainder of the sec- 

 tions. The only beds below the plant-beds which have been actually 

 correlated by their fossil contents with those in other areas are the 

 Bala and Lower Llandovery beds ; hence, at present, the evidence 

 goes to prove that they must be older than the Wenlock, and newer 

 than the Lower Llandovery. In Mr. Ruddy's paper * the Lower 

 Llandovery beds are said to be represented in this area by the Corwen- 

 grit series of Prof. Hughes ; and the latter, in summing up the 

 evidence as to the succession in this section, says it goes to prove : — 

 " that the Corwen grits are distinct from the Pen-y-Glog grits ; that 

 there is more evidence of a discordancy at their base than at the 

 base of the pale slates or the Pen-y-Glog grits; that there are 

 generally some beds of conglomerate, sandstone, or limestone with 

 sandstone on the horizon of the Corwen grits ; that the general 

 facies of the few fossils obtained from these beds in the district 

 examined is that of May-Hill rocks "f . 



He states, further, that these Corwen grits are succeeded by beds 

 which " pass up into the ' pale slates ' of the Survey, which in turn 

 pass up into the striped flaggy beds of Pen-y-Glog, on the top of which 

 come grits, to be referred to the true Denbigh Plag and Grit series." 

 As the latter are the higher beds mentioned where plants were 

 obtained, we have ample evidence of their position in regard to the 

 succession exhibited here, both from beds below and from those 

 which rest upon them. In other areas the position occupied here 

 by the Denbighshire flag and grit series, the pale slates, and the 

 Corwen grits seems to be chiefly filled up by the Llandovery or May- 

 Hill group and the Tarannon slates : the latter, I think, with the late 

 Mr. Salter, however, should always be included in the May-Hill 



* Quart. Journ. Geol. Soe. vol. xxxv. p. 200. 

 t Ibid. vol. xxxiii. p. 207. 



