290 THE CANADIAN NATURALIST. [Vol. vi. 



South \Yales, 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 confirmed by Ramsay and by Sedgwick. 

 [Ibid, 4, 236.] The May Hill s mdstone often includes, near its 

 base, conglomerate beds made up of the ruins of the older forma- 

 tion. To the north-east, in the typical Silurian country, it is of 

 great thickness and continuity, but gradually thins out to the 

 Bouth-west. 



There exists, moreover, another region where not less curious 

 discoveries were made. About forty miles to the eastward of the 

 typic-il region in South Wales appear some important areas of 

 Silurian rocks. These are the Woolhope beds, appearing through 

 the Old Red sandstone, and the deposits of Abberley, the Mal- 

 verns 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 Sjjstem 

 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 Mur- 

 chison had re^'arded as Llandeilo, or rather as the beds of 

 passage from Llandeilo to Cambrian, and had compared with the 

 north-west parts of the Caermarthenshire sections, (Sil. Sys. 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 Prof. John Phillips, 

 [Mem. Geol. S,ur. II., part 1.] 



What then was the value and the significance of the Silurian 

 sections of Murchison, when examined in the light of the results 

 of the Government surveyors ? The Llandeilo rocks, having 

 throughout the characteristic Orthis so much insisted upon [by 

 Murchison, were shown to be the base of a great conformable 

 series, and to the eastward, in Shropshire, to rest on the upturned 

 edges of the Longmynd rocks ; while westward, near Bala, they 

 overlie uncouformably the Lingula-flags, and in the island of 



