part 3] silurian hocks of the clux-forest district. 227 



upper part the shales have a very characteristic feature : in hand- 

 specimens they are well laminated with alternate light and dark 

 Laminae, which thus impart a striped appearance to the whole. They 

 contain few fossils, but Dayia navicula occurs in several places. 

 Along with this form Cardiola interrupta, Orthoceras tracheale, 

 and a small trilobite have been obtained. These beds are distinct, 

 both as regards litholog}" and fossil-content, from the succeeding 

 strata, and correspond to the Dayia Shales of the Ludlow district. 



The junction between the Dayia Shales and the ^Rhynchonella 

 Beds is not well marked, but some bands of massive, hard, blue 

 flagstone usually occur about this horizon. 



A few remarks on the apparently anomalous variation in thickness 

 of the Aymestry Limestone may not be out of place here. The 

 Limestone, which is about 100 feet thick at Ludlow, thickens 

 westwards to 250 feet at Mocktree Hill — only 6 or 7 miles 

 east of Bucknell — and, while known to occur at Pedwardine 1 

 (immediately east of the Church-Stretton Fault near Bucknell). it 

 has absolutely disappeared in the area here mapped. 



Determinations of Calcium Carbonate in Ludlow Rocks. 





I. II. III. IV. V. 



VI. 



Calcium carbonate 



Insoluble residue 



30% 



70% 



85° 22% 

 15% 78% 



25% 22% 

 75% ! 78% 



15% 

 85% 



1. Aymestry Limestone, Mocktree Hill. 



Block in tresb condition, with characteristic fauna of Conclidium Tcnightii 

 and Atrypa reticularis. 

 II. Aymestry Limestone, Pedwardine. 



A band of nodular limestone with abundant corals (Halt/sites, Favosites, 

 etc.). One of the persistent bands of true limestone. 



III. Dayia Beds, road from Chapel Lawn to Pentre Hodrey. 



Massive dark shale. 



IV. Rhynchonella Heds, near Chapel Lawn. 



Hard, blue, massive flagstone at the base of the beds. 

 V. Rhynchonella Beds, Selley Cross. 



Typical specimen from the upper part. 

 VI. Chonetes Beds, Hodrey Hill. 

 Typical specimen. 



The above determinations of the amount of calcium carbonate 

 present in the various Ludlow rocks have revealed the following 

 interesting facts : — 



(1) The bulk of the Aymestry Limestone with its typical fauna at Mocktree 

 Hill is only slightly more calcareous than the Rhynchonella or Chonetes Flags 

 of Clun Forest. 



(2) The Aymestry Limestone at Mocktree Hill is really a calcareous flag- 

 stone, with certain bands richer in lime and forming true limestone. Some of 

 these bands persist on the west, one being exposed in the faulted inlier 

 of Pedwardine, and another being recorded from near Bishop's Castle.' 2 



A. H. Cox, Q. J. G. S. vol. lxviii (1912) p. 371. 

 Caradoc Club, ' Eecord of Bare Facts ' 1892, p. 23. 



