1853.] RAMSAY — LOWER PAL^OZOICS OF N. WALES. 175 



band of rock to the Caradoc formation. The fossils it contains, as 

 noted by Professor E. Forbes, are mentioned in the Journal of the 

 Society, vol. iv. p. 297-299. They are generally the same as those 

 in a band of limestone that occm'S between the Caradoc Sandstone 

 and the Wenloek shale west of Wenlock edge. These fossils have 

 always been considered as characteristically " Caradoc," nevertheless 

 the rock that contains them is physically connected with the Wenlock 

 shale. It is conformable with the Wenlock beds and rests uncori- 

 formably on the Caradoc Sandstone, and (associated with the Wen- 

 lock shale) it entirely overlaps the latter in a distance of less than 

 two miles between Acton Scott and the Longixtynds. It was the 

 sandy and pebbly beach of the Wenlock sea ; and, just as in the 

 Llandeilo flags at Castell Craig Gwyddon, in Caermarthenshire, and 

 other places, where sandy and pebbly Caradoc-looking beds occur, 

 there is an occurrence of Caradoc Sandstone fossils, so in this coarse 

 littoral development of part of the Wenlock series the life of the 

 Caradoc times seems for a season to have been partially prolonged. 

 The typical Caradoc Sandstone of Shropshire is essentially a sandy 

 deposit, and seems to have been mostly accumulated in shallow v/ater. 

 Under similar conditions, whether in Llandeilo Flag pebble banks or 

 in Wenlock beaches, Caradoc-looking assemblages of fossils may 

 occur. In such cases they form an exceptional development ; they 

 are not the rule, for the mass of the Wenlock shale is a deep sea 

 deposit. The Longmynd and Shelve country (Llandeilo) stood above 

 water when it began. They were gradually depressed, and, as the 

 depression progressed, the beach crept inland until the old island 

 was entirely encased and buried under the Wenlock shale. The 

 outlying patches of sandstone, therefore, on the high land near the 

 Bog Mine, Shelve, are part of a Wenlock beach of somewhat later 

 date than the conglomerates and limestones that underlie the Wenlock 

 shale at lower levels on the south of the Longmynd. Scattered 

 pebbles of these rocks (the remains of denudation) strew many parts 

 of the surface of the Shelve country and of the Loiigmynds. 



It must always be borne in mind that the relative height of the 

 Longmynds to the Wenlock sea was very different from that which 

 the rocks on the opposite sides of the fault now maintain to each 

 other. The Church-Stretton fault is a downthrow on the west of at 

 least 2000 feet, and, the fault having taken place at a late geological 

 period, the Longmynds were probably at least 2000 feet higher (as 

 regards the Wenlock rocks, while these were being deposited), than 

 the height they now maintain with reference to that formation. This 

 would materially modify the conditions of deposition, and the Long- 

 mynds must have stood out amid the waters as a bold and rocky islet, 

 from the waste of which in part the Wenlock littoral sandstone beds 

 of Shropshire were derived. 



Denudation. — The denudation which North Wales and parts of 

 Shropshire have undergone is of vast amount. To describe it fully 

 would itself occupy a long memoir. It is worthy of remark, how- 

 ever, that, as shown in the Shelve and Longmynd country and in 

 the neighbourhood of Builth in Radnorshire (see Sections of the 



