202 



AYMESTRY OR LUDLOW LIMESTONE. 



from one to five feet thick, dipping to the south and south-east at slight angles ; the 

 laminae of deposit being marked by layers of shells and sometimes of corallines. When 

 quarried into, the rock is of an indigo or bluish grey colour, in parts mottled by the 

 mixture of white carbonate of lime, both crystalline and compact. The quarries, like 

 those in all the other rocks of the Ludlow formation, present natural backs more or 

 less vertical, usually coated by a dirty yellow or greenish shale. The faces of these joints 

 usually exhibit lines of small cavities similar to those already described in the upper 

 Ludlow rock. When first laid bare in quarries, they have often a weathered aspect, 

 which we may account for by supposing that they have for a long time been permeable 

 to water. 



This limestone constitutes the prominent and frequently the highest part of the 

 escarpment of the Ludlow formation, in those hills which, beginning at Sutton near 

 Wenlock, rise into the elevated ridges extending by Larden and Siefton to Mocktree 

 Forest. It also forms the highest edges of the opposite escarpments of the Ludlow 

 promontory. (See PI. 31. fig. 5.) 



Throughout this range, these calcareous beds are variously inclined according to the 

 positions into which the Ludlow formation has been thrown. The prevailing inclination 

 is small, but there are many marked exceptions to this arrangement, particularly around 

 the Ludlow promontory. These will be more specially alluded to in the nineteenth 

 chapter, when the dislocations of the strata are described. 



In nearly all the quarries situated between Norton Camp and Aymestry, the rock 

 is charged with a profusion of that remarkable shell called the Pentamerus Knightii. 

 (PL 6. fig. 8.) This species is confined almost exclusively to the limestone of this sub- 

 division, having never been found in the Upper, and very sparingly in the Lower Ludlow 

 Rock 1 . The following fossils also characterize the calcareous zone: Lingula Lewisii, PI. 6. 

 fig. 9 ; Terebratula Wilsoni, fig. 7 ; Bellerophon Aymestriensis, fig. 12 ; Avicula reticulata, 

 fig. 3 ; and the corals Favosites Gothlandica, &c. These fossils, with the Atrypa affinis 

 (Terebratula affinis, Min. Con.) PL 6. fig. 5, serve to mark the course of the central 

 subdivision of the Ludlow formation where the Pentamerus Knightii disappears. I 

 have before observed that the cap of the limestone is charged with the Terebratula 

 Navicula (PL 5. fig. 17.). 



In the range of hills north of the river Onny, this limestone is principally worked at Dinchope 

 and at Norton Camp. At the former place it appears as several undulating and disrupted masses, 



of the limestone without producing confusion, since in the same district there is another place called Downton, 

 the seat of Sir W. Boughton, Bart., which, as we have seen, is the site of limestones in the Old Red Sand- 

 stone. The Aymestry limestone, as will hereafter be shown, occurs at Sedgely in Staffordshire, where it is 

 largely used ; but a name derived from a distant outlier, the relations of which could not have been established 

 without the evidences we are now considering, is quite inadmissible. 



« A single specimen of this shell has been detected in the Wenlock limestone of Nash, near Presteign, by 

 Mr. Davies. (See chapters on Radnorshire and the organic remains.) 



