360 CAMBRIAN AND SILURIAN IN EUROPE. [XV. 



beds. Again, in South Wales, near Builth, the May Hill 

 sandstone or Upper Llandovery rests upon Lower Llandeilo 

 beds ; while at Noeth Grug the overlying formation is traced 

 transgressively from the Lower Llandovery across the Caradoc 

 to the Llandeilo. These important results were soon con- 

 firmed by Ramsay and by Sedgwick. (Ibid., 4, 236.) The 

 May Hill sandstone often includes, near its base, conglomerate 

 beds made up of the ruins of the older formation. To the 

 northeast, in the typical Silurian country, it is of great 

 thickness and continuity, but gradually thins out towards the 

 southwest. 



There exists, moreover, another region where not less curious 

 discoveries were made. About forty miles to the eastward of 

 the typical region in South Wales appear some important 

 areas of Silurian rocks. These are the Woolhope beds, appear- 

 ing through the Old Red sandstone, and the deposits of 

 Abberley, the Malverns, and May Hill, rising along its eastern 

 border, and covered along their eastern base by the newer 

 Mesozoic sandstone. The rocks of these localities were by 

 Murchison in his Silurian System described as offering the 

 complete sequence. When, however, it was found that his 

 Caradoc included two unconformable series, examination showed 

 that there was no representative of the older Caradoc or Bala 

 group in these eastern regions, but that the so-called Caradoc 

 was nothing but the Upper Llandovery or May Hill sandstone. 

 The immediately underlying strata, which Murchison had 

 regarded as Llandeilo, or rather as the beds of passage from 

 Llandeilo to Cambrian, and had compared with the northwest 

 parts of the Caermarthenshire sections (Silurian System, 416), 

 have since been found to be much more ancient deposits, of 

 Middle Cambrian age, which rest upon the crystalline hypozoic 

 rocks of the Malverns, and are unconformably overlaid by the 

 May Hill sandstone. We shall again revert to this region, 

 which has been carefully studied and described by Professor 

 John Phillips. (Mem. GeoL Sur., II. Part I.) 



What then was the value and the significance of the Silurian 

 sections of Murchison, when examined in the light of the 



