60 Dr. J. E. Marr—The Ashgillian Series. 
“Upper Bala Group, Sedgw. (restricted in 1866). The Upper Bala 
of the synopsis includes the Bala Limestone, now Ihddle Cambrian. 
“1, Hirnant Limestone and Llanfyllin Beds, viz., pale-coloured 
slates above the Bala Limestone. Ash Gill slates, etc., above the 
Coniston Limestone. 
“2. Llandovery Rocks (Phillips, Salter, Lyell—Lower Llandovery of 
the Survey).” 
The same classification is given in somewhat different words on 
p. 26 (text). 
With regard to the sess ie of the term in 1866 I have searched in 
vain for any printed record of such restriction, and believe that it was 
the result of conversation between Sedgwick and Salter, for in a note 
on p. 26 of the Catalogue Salter writes: ‘‘ Prof. Sedgwick trusts me 
to arrange them [the Bala fossils] according to the present state 
of our knowledge, 1867. The Bala Group or Upper Cambrian of 
Sedgwick therefore consists of :— 
Lower Bala = Llandeilo Flag (Upper Llandeilo, Geol. Survey, the 
Rene Arenig being the lower). 
Ginnie aces Made Bala = Caradoc Sandstone and Bala rocks (Geol. Survey and 
Sad ir R. I. Murchison). : 
mess.) Upper Bala = Caradoc shales, Hirnant Limestone, and Lower 
Llandovery rock (Geol. Survey).”’ 
It is clear to me that the Upper Bala as defined by Salter in the 
paragraph I have quoted is very different from the Ashgillian as 
I propose to use it, so far as the Bala region is concerned, for he 
definitely takes the base of the Hirnant Limestone for its base, whereas 
I propose to include beds some way below this limestone, which beds, 
I hope to show, are equivalent to the Ashgill Beds, which Salter 
includes in the Upper Bala. 
The position of the summit of the Upper Bala Group as defined by 
Salter is even more unsatisfactory. We have seen that he divides the 
Upper Bala Group into two sub-groups, viz., the Hirnant Limestone, 
etc., below, and the Llandovery above. 
Salter himself says of them (Cat. Camb. and Sil. Foss., p. 72): 
‘“‘The fossils of these two divisions are arranged together, as it is 
clearly impossible always to draw a line between them; they form, 
indeed, one series. But the list is kept in two separate columns here, 
as each group contains a few peculiar species.” 
The Llandovery Beds here mentioned (now called Lower Llandovery) 
are at the present day, by general consent, bracketed with the May 
Hill Beds (Upper Llandovery) to form the basal series of the Silurian 
system. We are therefore concerned with the rocks containing the 
fossils placed by Salter in the columns of the Catalogue headed 
““Upper Bala proper.’”’ Twenty-two forms are recorded in these 
columns. The first entry, Medulites favus, is clearly placed in the 
wrong column owing to a clerical error. Two trilobites are given, 
viz. Phacops obtusicaudatus and Proetus sp., from Coldwell and the 
equivalent strata of Helm(s) Knot, Dent. Salter elsewhere (Cat., p. 26) 
brackets these Coldwell Beds with the Ashgill Beds—an extraordinary 
error, the Coldwell Beds actually belonging to the Lower Ludlow 
1 The word Cambrian is clearly a misprint for Bala. 
