ANNIVERSARY ADDRESS OF THE PRESIDENT. 



I29 



and place them in his Lower Bala group. The Bala group, or 

 Upper Cambrian of Sedgwick, consists therefore of 



f Lower Bala= Llandeilo flags (Upper Llandeilo of the 

 j Geological Survey, the Arenig being the Lower). 

 Upper J Middle Bala=the Caradoc Sandstone and Bala rocks 

 Cambrian*. ) (Geological Survey and Sir R. Murchison). 



I Upper Bala = the Caradoc Shales, Hirnant Limestone, 

 ^ and Lower Llandovery rock (Geological Survey). 



The Upper Llandovery or May-Hill Sandstone un conformably over- 

 lies these. 



Sedgwick's Middle Bala, and part of the Upper, are therefore 

 equivalent to the true Caradoc of the Geological Survey ; and as 

 such I treat that group here ; or the Middle Bala of the Cambridge 

 Catalogue will embrace the whole of the 600 species known as 

 Caradoc forms. I have already discussed the Llandeilo formation 

 proper iu the sense now used by the Geological Survey, having 

 relegated those species hitherto called Lower Llandeilo to the Arenig 

 group — the Middle Cambrian of Sedgwick?. The Lower Bala 

 includes certain dark earthy slates and bands of limestone occurring 

 on the east flank of the Arenigs, Mynydd Tarw and Craig-y-glyn 

 above Llanarmon in the Berwyns, the black slates on the flanks of 

 Snowdon, also the arenaceous deposits on the west side of Bala Lake 

 below the Bala Limestone, and that limestone also. 



The Middle Bala group of the Woodwardian Catalogue embraces 

 the Bala Limestone and its associated sandstones and slates in North 

 and South Wales. In Shropshire it is the Caradoc Sandstone, with 

 its Horderley Limestone. The Coniston and Kildare limestones, and 

 the Craig-Head and Peebles limestones, are all of this age J. 



Sedgwick's " Upper Bala " comprehends the Aber-Hirnant beds 

 above the Bala Limestone (with peculiar fossils), the lower part of 

 the Coniston Mags (that conformable to the limestone), and all beds 

 above the Bala Limestone and beneath the May-Hill Sandstone. 

 Again, the " Upper Bala " includes all the beds, whether near 

 Meifod or Welchpool or Llanwyddyn, which lie above the Bala 

 Limestone and under the unconformable cover of the Denbighshire 

 grit and flag. In ascending order the Upper Bala includes 



1. The Hirnant Limestone and slate = Coniston Flags, 

 lower part only (Ashgill, Coldwell, &c), above 

 the Coniston Limestone, 

 f S lo- * V\ I ^* I^ an d° ver y beds (Lower Llandovery of Murchison) 

 ^ 1 =the Mathyrafal Limestone, near Meifod, of 



1^ Sedgwick. 

 " It is the great fossiliferous group of Haverfordwest. The 

 Daiquorhan and Mullock beds in Ayrshire, the fossiliferous rocks of 

 Maume and Cong in Galway belong in part to it"§. 



* Vide Woodwardian Catalogue. Cambridge, pp. 25, 26, &c. 

 t Consult the table of equivalents of the strata underlying the May-Hill 

 Sandstone, Woodwardian Catalogue, p. 25. 



\ Vide Woodwardian Catalogue, pp. 26, 39. § Log. cit. pp. 26, 72. 



Upper 



