Vol. 52.] LLANDOVERY AND ASSOCIATED ROCK8 OP CONWAY. 277 



There are two main faults in this district : one (F. 1), as has 

 been mentioned above, forms our boundary-line to the W. and strikes 

 10° W. of N. ; while a second one (F. 2), striking 30° S. of W. and 



Section through A.B 



Lodge. Road. River 



Conway- 



Section through CD. 



with a downthrow to the E., brings the Upper Llandovery and 

 Tarannon beds against the Wenlock Shales. We believe that the 

 occurrence of Upper Llandovery Beds is dependent in a great 

 measure on this second fault. 



IV. Detailed Description op the Beds. 

 1. The Llandovery Rocks. 



Rocks which are undoubtedly of Llandovery age occur on the 

 right bank of the Afon Gyffin, from opposite Neckarmount House to 

 the timber-yard buildings. Farther W. they are concealed beneath 

 the alluvium of the river. They strike 10° N. of W., and dip 10° W. 

 of S. at an angle of about 55°. Continuing on this strike, they are 

 again seen in vertical section in the high bank opposite the fork 

 formed by the junction of the Benarth and Gyffin roads ; here they 

 occur slightly below the level of the road, and probably occupy the 

 whole of the marshy ground lying between the road and the bank. 



(a) Stream-section. — The beds seen in section near the stream are 

 capable of the following subdivisions, in descending order : — 



7. Hard grey bed. 



6. Black shale-band, with Bastrites maxvmus. 



5. Grey flagstones. 



4. Black shale-band, with graptolites. 



3. Grey flagstones. 



2. Black shale-band, with graptolites. 



1 . Very tough flagstones. 



1. Towjh Grey Flagstones. — Little need be said of the tid- 

 fossiliferous beds forming the base of the section. They consist of 

 tough grey flagstones, and are well exhibited in the bed of the 



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