SILUEIAN GROUP. 



121 



SILUEIAN GROUP. 



ill. 



Ladlow Formation. . . 2. Wenlock Formation. 



1. Caradoc Formation. . . 2. T.landeilo Formation. 



This Group, (which derives its name from the ancient 

 kingdom of the Silures, a tract of country where these rocks 

 are best developed,) extends over a considerable area in 

 the border counties of England and Wales, as well as over 

 a large portion of the principality itself. The sedimen- 

 tary deposits comprise argillaceous, calcareous and arena- 

 ceous beds, varying both in colour and texture. Some of 

 the sandstones are fine-grained or gritty. The limestones 

 are argillaceous, concretionary and sometimes flaggy. The 

 following summary and subjoined localities are abstracted 

 from the ' Silurian System' of Sir R. I. Murchison, to whose 

 large work the reader is referred for full details connected 

 with the whole district of Siluria. 



