24. 



CHAPTER XVII. 



UPPER SILURIAN ROCKS (continued). 



2nd Formation "Wenlock Limestone," Equivalent "Dudley Limestone" (See 

 Map and PL 31. figs. 2, 3, 4 and 5, and e and/ of wood-cut, p. 196.) 



THE Ludlow rocks occupying the chain of hills between the Onny and the Severn are 

 succeeded on the north-west by a sharp rectilinear ridge, near twenty miles in length, 

 called " Wenlock Edge." The strata of which this ridge consists rise at a slight angle 

 from beneath the Lower Ludlow Rock ; the inferior portion of the latter being soft, 

 has been so denuded as to form a valley between the harder masses of Ludlow rock on 

 the one side, and Wenlock limestone on the other. These relations are distinctly seen 

 in the form of the country as represented in the vignette at the head of the chapter. 



a The high ridge of upper Ludlow rock and Aymestry limestone. b The Wenlock Edge, the intervening valley having 

 been excavated in the lower Ludlow shale. c The valley of the Wenlock shale. 



The Wenlock limestone is in every respect identical with the well-known rock of 

 Dudley, and contains the same organic remains. Here, however, it exhibits relations 

 to the superior and inferior strata which do not exist at Dudley, and hence the name of 

 " Wenlock " has been preferred 1 . 



1 At Dudley, as will hereafter be shown, the limestone being abruptly protruded through the coal measures 

 without the great connecting links of Ludlow rocks, Old Red Sandstone, and carboniferous limestone, no 

 evidence whatever can there be obtained to prove its place in the geological Series ; in Shropshire, on the con- 

 trary, a clear order of superposition exhibits all the passages and relations required, establishing the place of 



