﻿Vol. 6 1.] ANNIVERSARY ADDRESS OE THE PRESIDENT. IxXXV 



fossils ; ' and, again (p. 39), Salter notes that Sedgwick's Middle 

 Bala ' group extends a short distance, probably a couple of hundred 

 feet, above the Bala Limestone. But it does not include the 

 Hirnant Limestone, which is the base of the Upper Bala group.' 



In view of this vagueness, it appears justifiable to draw the 

 line between the Caradocian and the Ashgillian, in accordance with 

 Sedgwick's statement that the Upper Bala has a peculiar set of 

 fossils. In this case it will include the Ehiwlas Limestone and 

 all other beds above the Bala Limestone, to the summit of the 

 Ordovician System. It is perfectly clear that, so long ago as 1847, 

 some member of the Geological Survey suspected from the faunas 

 that the Ehiwlas Limestone was not the Bala Limestone ; for there 

 is a sentence, in one of Jukes's letters of that date, which shows 

 that some one maintained that the limestone at Creigiau Isaf was 

 Ehiwlas and not Bala Limestone. 1 



By utilizing this marked contrast between the Caradocian and 

 Ashgillian faunas we can subdivide the Ashgillian rocks of North 



Wales as follows : — 



(Hirnant Limestone. 

 Shales. 

 Ehiwlas Limestone. 



The fauna of these Ashgillian strata is so very different from 

 that of the Caradocian that one cannot have the least hesi- 

 tation in assigning them to a different series, and as the beds are 

 not known in the type-area of Caradocian deposits, it would be 

 altering the signification of the term Caradocian in a marked 

 degree to add them to the Caradocian Series. 



The beds are well represented in the Lake District, and as 

 we find the term Ashgill Beds used and defined in Sedgwick's 

 Catalogue (p. 72) — ' I arrange Ashgill Beds (above the Coniston 

 Limestone) with this division/ that is the Upper Bala division, — it 

 may be well adopted as the name of the series, for the limit drawn 

 here between the Middle and the Upper Bala of Sedgwick is exactly 

 that which I would desire to see adopted between the Caradocian 

 and the Ashgillian Series. 



In my paper on the Coniston-Limestone Series, to which refer- 

 ence has been already made, I gave some account of the development 

 in Britain and Scandinavia of the strata of this series. In that 

 paper the beds of Keisley were placed in the Sleddale Group, which 

 is Caradocian ; but, after reading Mr. F. E. C. Eeed's paper on the 



1 See ' Letters of J. Becte Jukes '1871 p. 293. 



