30 PALEOZOIC TIME. [CHAP. III. 



Staffordshire which is traversed by the section, nor over 

 Warwickshire, where Coal-measures rest on Cambrian 

 shales. We may assume, therefore, that this district was 

 dry land during the whole of Ordovician time, that the 

 Longmynd and Caradoc tracts formed part of the land 

 area in Arenig and Llandeilo times, but were submerged 

 toward the close of the period, and covered by the Caradoc 

 sandstones and shales. The fact of quartz-felsite, like that 

 of Charnwood, having been found below the Lias near 

 Kettering, seems to indicate that this land tract had a still 

 further eastward extension. 



In Anglesey and Carnarvon the pre-Cambrian ridges 

 which formed land throughout Cambrian times were still 

 further submerged, and, perhaps, eventually were over- 

 topped by the waves of the Ordovician sea. The exact age 

 of the earliest fossiliferous deposits of Anglesey is not yet 

 quite settled, but the probability is that the fossils in the 

 lowest grits are not of earlier date than the Arenig, and 

 Dr. Callaway thinks that at this time the northern and 

 central parts of the island were still above water. 



" The basement conglomerates contain not only boulders 

 from the granitoidite, but also pieces of halleflinta, such as 

 we find east of Llanfaelog, and numerous fragments of 

 purple and green shale, very similar to types characteristic 

 of the tract west of Malldraeth Marsh. . . . The western 

 area furnishes similar evidence; the large angular frag- 

 ments in the Tywyn conglomerate cannot have travelled 

 far, and the pieces of altered shale in the Clymwr conglo- 

 merate must have been derived from the neighbouring land 

 to the west." l In other parts of the island beds of Bala 

 age have been found, and these probably extended much 

 farther west, and were, perhaps, continuous with beds of 

 the same age in the west of Ireland. 



In the Lake District we again find a thick series of 

 1 Callaway in " Quart. Journ. Geol. Soc.," vol. xl. p. 582. 



