﻿576 DE. T. GBOOM AND ME. P. LAKE ON" THE [NoV. I908, 



formity, and the break appears to be purely local. It may be due 

 to irregularities of deposition, such as commonly occur m sandy 

 beds ; or it may possibly be the result of a strike-fault of low dip. 



Fig. 11. — Section shown by excavation in Ncmt Llafar. 



'bands! 



The fauna of the Glyn Grit and Limestone is very similar to that 

 of the Dolhir Series, although not quite so rich. In the small pits 

 on Mynydd Fron Frys, where there is a limestone below and grits 

 above, corals are the predominant fossils. In the roadside above 

 Plas Lleucu, and at Pant-y-graig, where soft chocolate-coloured beds 

 are intercalated among the grits, gasteropods are abundant. But 

 few of the species are confined to this horizon, and by far the 

 greater number occur also in the beds below. 



At Corwen, the fact that the Corwen Grit is overlain with 

 apparent conformity by beds that contain graptolites of Lower 

 Birkhill age, led us to conclude that the grit also is Llandovery, 

 although in that district we found no fossils in it. At Glyn we have 

 not found the graptolitic shales ; but fossils are by no means rare in 

 the grit. These fossils, however, do not differ from those of the 

 Dolhir Beds below, and on the other hand are quite distinct from 

 those of the Fron-Frys Slates above. Moreover, the upper part of 

 the Dolhir Beds is sandy, and contains, calcareous nodules ; and it 

 is sometimes very difficult to draw a precise line between the two 

 series. We therefore include the Glvn Grit with the Dolhir Beds 



