Dr. J. E. Marr—The Ashgillian Series. 69 
The difference of opinion as to what line should be taken as 
separating the Ordovician from the Silurian requires fuller 
consideration. Professor Lapworth in the Moffat district places the 
lowest zone of the Birkhill Shales, that of Diplograptus (Cephalo- 
graptus) acuminatus, in the Silurian, while Tullberg assigns the 
corresponding zone in Scania to the Ordovician, because it, like the 
Scotch zone, has no Monograpti. Lithologically and paleontologically, 
however, it seems to be more closely related to the overlying beds 
than to those beneath it, and I would follow Lapworth in assigning it 
to the Silurian. 
In North Wales the question is not so easy. The Hirnant Lime- 
stone is not a richly fossiliferous deposit, its most frequent fossil being 
Orthis hirnantensis. Salter, as we have seen, referred it to the Upper 
Bala, while Professor Hughes has maintained that two deposits have 
been referred to this division, the lower of which is Ashgillian and the 
upper Llandovery. The question remains to be settled. 
It may be remarked that the Llandovery Beds of Wales and the 
Welsh borders still require much work. Professor Hughes has 
separated the fossils of the Upper and Lower Llandovery Beds of the 
typical area, and his collections are preserved in the Sedgwick 
‘Museum, but his observations require extension in surrounding areas. 
My objects in this paper have been to show that the Ashgillian 
Beds form a group sufficiently important to be separated as a series 
from the beds of the Caradocian Series below; to prove that the term 
Upper Bala applied by Salter was too vaguely defined to stand (even 
were the term not objectionable on other grounds), and that therefore 
another term is required, that of Ashgillian being adopted because the 
term ‘‘ Ashgill Beds”? used by Salter for his Upper Bala Beds in the 
Lake District was applied to a definite group well defined by him; 
lastly, to indicate to future workers the lines on which to proceed in 
giving us what we greatly require, a monograph upon the stratigraphy 
and paleontology of this important series. 
TABLE OF THE ASHGILLIAN STRATA OF THE BritisH IsLEs. 
Sour Waxes. Norra Waxzs. N.or ENGLAND.) GIRVAN. | IRELAND. 
| Phyllopora- | 
| _Hirnant | Beds of 5 5 
Sha By Limestone ? | Backside Beck, | : | ‘ 
| | Sedbergh ? 
| | 
| Mueronatis- 
Redhill Beds. | Beds ot Conway.) 4 noi Shales. | L24Y>u™ | Tirnaskea Beds. 
= Shales near S | Shales. | 
Maeshir ? | 
| Staurocephalus- | Salley Ee ceegae 
Sholeshook Rhiwlas Limestone | Starfish pee Sel 
Limestone. Limestone. (with Keisley | Bed. fie eee ae 
Limestone). | =Portraine Lime- 
stone. 
