MAY HILL SERIES. 8/ 



fess the difficulty of separating them in the field. Therefore they 

 are best grouped together in the May Hill Series, which includes 

 also the Tarannon Shales.' 



Sir Andrew Ramsay has pointed out that physically the break 

 between the Llandovery beds and the strata below is complete. In 

 Shropshire and at Builth the unconformity is visible, and in the 

 Malvern area the beds lie on Upper Lingula flags. The Upper 

 Llandovery beds on the banks of the Onny lie on the higher part 

 of the Caradoc Sandstone, and as they strike northward, gradually 

 overstep the higher strata, till, on the banks of the Severn, near 

 Buildwas Abbey, they rest on the lower beds of the same formation. 

 A few miles from Wenlock Edge they lie on the nearly vertical 

 edges of the Longmynd rocks, and also on various members of the 

 Cambrian system, between Church Stretton and Chirbury. (See 

 Fig. 9, p 58.) In South Wales, between Builth and Newbridge, 

 they lie equally unconformably on the Llandeilo flags ; and 14 miles 

 off at Noeth Grug they rest on the Lower Llandovery beds ; but, 

 again, they rapidly creep across these to the south-west, and in 

 the river Sawdde the Llandovery beds lie directly on the Llandeilo 

 flags. There is no unconformity so complete as this yet observed 

 in other members of the strata from the Llandeilo flags upward.^ 



The Silurian strata are not exposed west of Llanarthney in 

 Caermarthenshire, being concealed by the Upper Old Red Sandstone 

 and Carboniferous strata, which overlap them and rest on the 

 Cambrian rocks. 



MAY HILL SERIES. 



This term is adopted from that used by Murchison in 1834 for 

 the older rocks of May Hill, between Newent and Mitcheldean, on 

 the borders of Herefordshire and Gloucestershire. 



The May Hill Sandstone, which is included in the series, was 

 originally grouped with the Caradoc Sandstone by Murchison, and 

 afterwards distinguished as Upper Caradoc by John Phillips, who 

 had observed the difference in organic remains between the two 

 Sandstones. Still later the distinctness of the May Hill Sandstone 

 from the Caradoc Beds was shown by Sedgwick and M'Coy.^ 



The series comprises the following divisions : — 



3. Tarannon Shales. 



2. Upper Llandovery Beds. 



I. Lower Llandovery Beds. 



^ Brit. Assoc. 1875 ; Trans. Cambr. Phil. Soc. iii. 255. See also Hicks, G. 

 Mag. 1876, p. 159. 



" Ramsay, Geology of North Wales, edit. 2, p. 5. 



^ Q. J. ix. 215 ; see also J. VV. Salter, G. Mag. "1867, p. 201. 



