Yol. 68.] AND CAMBEIAN INLIER AT PEDWARDINE. 371 



fact that the Bictyonema Shales and the Wenlock Shales, which are 

 there brought into contact one with the other, give rise to such 

 similar ground. 



Within the inlier the relation of the Dictyonema Shales to the 

 Brampton Grrits and Conglomerates is nowhere displayed in section. 

 As previously remarked, the strata of both these series are highly 

 inclined to the west, so that the Dictyonema Shales dip towards the 

 Brampton Beds. The boundary between the two formations follows 

 a very sinuous course, too complex to explain by normal faulting. 

 This sinuous boundary would represent exactly the outcrop of a Yevy 

 gently inclined thrust-plane dipping about north-north-westwards. 

 This leads to the conclusion that the Brampton Grits and Conglome- 

 rates have been thrust from the north-west on to the Cambrian. 

 The thrust is obviously earlier than the north and south post- 

 Silurian faults which bound the inlier ; and, since the neighbouring 

 Letton Beds rest almost horizontally and show no signs of dis- 

 turbance, it is possible that the thrust is of pre-Bala date. If this 

 be the case, then the movement which tilted the Letton Beds east- 

 wards would have the effect of making the thrust-plane appear 

 more nearly horizontal than it was originally. 



It is noteworthy that, whereas no sign of any great disturbance 

 is seen among the Wenlock Shales on the east of the inlier, the 

 Ludlow Beds on the western side are everywhere much folded and 

 show signs of a considerable amount of overthrusting. It would 

 thus appear that this inlier is only the faulted remnant of a much 

 larger mass, which served to protect the country on the east from 

 the effects of the post-Silurian pressures arising in the west. 



Occurrence of Aymestry Limestone. 



Owing to a branching of the western boundary-fault at the 

 southern end of the inlier, a small strip of Aymestry Limestone is 

 let in between Wenlock Shales and Lower Ludlow. It is to these 

 beds that the words ' Nodular Limestone, Corals,' printed on the 

 1-inch Geological Survey map, doubtless refer. 



This occurrence is interesting, as affording a last glimpse of the 

 Limestone before its complete disappearance in the west. It is seen 

 in two small disused quarries to be only a few feet thick, and 

 nodular and very impure in character owing to the abundance of 

 shaly partings. It yields Conchidium JcnigTitii, Rhynchonella nucula, 

 numerous corals (Favosites, Beliolites, etc.), and is underlain by 

 shales with ill- preserved graptolites, the whole series dipping 

 eastwards at an angle of 10°. 



VI. Summary. 



1 . The inlier of Pedwardine consists mainly of Brampton Grits and 



Conglomerates and Bictyonema (Upper Cambrian) Shales. 



2. The Brampton Grits and Conglomerates are referred to the 



Longmyndian. 



