﻿Vol. 64.] BALA AND LLANDOVERY EOCKS OF GLYN CJEIRIOG. 591 



Group ; but he now/ like Mr. F. E. C. Reed, places it in 

 Group III, and accordingly some alteration is necessary in the list 

 of fossils given in his former paper. He also places the Phyllopora- 

 Beds of Backside Beck above the true Ashgill Shales, but includes 

 them in the same group, which he calls the Ashgillian. 



Turning to the lowest or Roman-Fell Group, it will be found that 

 it consists of ashes, ashy shales, and nodular limestones, the latter 

 often composed almost exclusively of the tests of Beyrichia. The 

 list of fossils is short ; but it includes Lingula tenuigranulata and 

 BelleropTion hilobatus, the former of which occurs in the Teirw Beds 

 and the latter in both the Teirw and the Bryn Beds. Trematis corona^ 

 another characteristic fossil of the Eoman-Fell Group, has not yet 

 been found at Glyn Ceiriog. The remaining species do not appear to 

 be especially characteristic; the palaeontological evidence is therefore 

 not very complete : but, so far as it goes, it points to the approxi- 

 mate equivalence of the Eoman-Fell Group with the Teirw Beds. 



Of the fossils in Dr. Marr's list from the Sleddale Group some 

 eighteen have been found in the Bryn Beds. Among the more 

 important forms that are common to the two we may mention 

 Tentaculites anglicus, Tetradella corivpUcata, Lichas laocatus, Chasmo^s 

 conicophthalma^' Ti'inucleus concentricus, Lingula ovata, Platystro- 

 pJiia biforata, Rafinesquma deltoidea, R. exjpansa, and Triplesia 

 spiriferoides. On the other hand, Dr. Marr's list (with the Keisley- 

 Limestone fossils omitted) includes Cyhele verrucosa, Encrinurus, 

 Eemopleurides, and Trinucleus seticornis, which in the Glyn district 

 we should look upon as characteristic of the Dolhir Beds. On the 

 whole, however, the fauna of the Sleddale Group is much nearer to 

 that of the Bryn Series than to the fauna of any other group in the 

 Glyn district ; and the fact that the top of the Bryn Series is cut 

 out by the Dolhir Fault may explain some of the discrepancies. 

 Further, as Dr. Marr informs us, it is possible that some of the 

 fossils recorded as from the Sleddale group, but not collected by 

 himself, may in reality belong to the Ashgillian. 



The Ashgillian Series of the Lake District is undoubtedly 

 represented by the Dolhir Series of Glyn, although it is possible 

 that neither the base nor the summit of the two exactly coincide. 

 There is the same abundance of cystideans in the calcareous beds, 

 and of polyzoa, including PTiyllopora Hisingeri, in some of the more 

 shaly deposits. The absence of Staurocephalus and PhilUpsinella 

 parabola at Glyn Ceiriog, and their presence both in South Wales 

 and in the Lake District, is somewhat remarkable. But over the 

 greater part of the Glyn area the base of the Dolhir Series, like 

 the top of the Pandy Group, is cut out by the Dolhir Fault and 

 the actual StaurocepJialu s-Limestone may be missing. We may 

 conclude, therefore, that the Dolhir Beds belong to the Ashgillian 

 Series ; but that, in all probability, the whole of that series is not 

 visible at Glyn Ceiriog. 



^ Geol. Mag. dec. 5, toI. iv (1907) pp. 59-69. 



- Phacops brevispina of Dr. Marr's list. The species described by Salter 

 as Ph. conicophthahna was supposed by Schmidt to be identical with his 

 Ph. brevispina ; but Salter's type shows the bases of long genal spines. 



