148 



DE. Li. L. ELLES OS THE BALA COUXTET: [vol. IxXYiii, 



On the east side of the track which runs between the Llanderfel 

 and Lake- Vrrnwy roads east of Y Grarnedd farmhouse, the trend of 

 the beds is practically at right angles to that of those on the ^Yest 

 side, against which they are obviously faulted. The Grelli-grin 

 Limestone has here an extensive outcrop, since it appears to be 

 just rolling over : it has, as usual, been quarried for lime, and has 



yielded the following fossils 



Ovthis fXicolellaJ actoniae (Sowerby). 

 Orthis fPlectorthisJ plicata 



(Sowerby). 

 Orthis (Dalmanella) elegantulatype. 

 Ortliis (Dalmanella) testudinaria 



type. 



Triplecia fCliftoniaJ sinriferoides 



(M^Coy). 

 Plectamhonites sericea (Sowerby). 

 Calymene caractaci Salter. 

 Chasmops macroura (Sjogren). 

 Monticulipora fibrosa (M'Coy). 



Lender the microscope the limestone is seen to be definitely 

 oolitic : this character is, however, only visible in hand-specimens 

 when thev have been verv m.uch weathered. L^nderlvinsj the 

 limestone the Calcareous Ash may be detected ; but it is not well 

 exposed, although the Pont-y-Ceunant Ash shows up beautifully 

 on a good dip-slope with the Allt-Ddu Mudstones underneath it. 



The Grelli-grin Limestone is also seen again near an old limekiln 

 on the north-east, nearer the river, with the lower beds beneath it 

 a little farther north : the relation between these two sets of beds 

 is rather obscure, but is suggestive of tear-faulting, with the tear 

 running east and west. 



The limestone is also apparently faulted westwards against the 

 Allt-Ddu Beds, which are overlain by the Pont-y-Ceunant Ash and 

 the Calcareous Ash, all three forming part of a small syncline. 



Bryn-cut and Gelli-griii. 



Part of the succession is clearly seen on the slopes of Bryn-cut. 

 although the outcrops of the different beds are shifted in places 

 by a series of tear-faults. The lower part of the hill on the 

 north side is occupied by the Allt-Ddu Mudstones, highly cleaved 

 as usual, except in a few harder more sandy bands : these slightly 

 harder beds make two well-defined little scarps of which the lower 

 is the more conspicuous (fig. 2, p. 1-42). Fossils occur throughout, 

 commonest forms being the following : — 



Ortliis (HeterortMs) alternata 

 (SoAverby) & rar. retrorsistria, 

 (DaTidson). 



Orthis (Dinorthis) flahellxdum 

 (Sowerby). 



Plectamhonites sericea (Sowerby). 



Strophomena fRafinesquinaJ ex- 

 panse. (Sowerby). 

 Strophomena (R.) gra ?ifZis (Sowerby). 

 Trinuclev.s gihhifrons M'Coy. 

 Trinncleus concentricus Eaton. 

 Asaphus poicisi Salter. 

 Calymene caractaci Salter. 



A short distance above the upper of the two scarps in the mud- 

 stones, another feature is formed by the Pont-y-Ceunant Ash, here 

 about 25 feet thick ; and about 50 feet of rock separate the ash 



