﻿64 ME. T. F. SIBLY OX THE FATJNAL SrCCESSION IX THE [Feb. I908, 



In addition to the main disturbance which determined this un- 

 conformity, minor movements during the formation of the Upper 

 Lonsdalia-beds are suggested by the peculiar nature of the bedding 

 in the lower part of the section. In one part of the sequence, the 

 truncated edges of a series of limestone-beds form a surface upon 

 which another series of beds, less steeply inclined, rests. This is 

 shown, although not very clearly, in the lower part of the photograph 

 (fig. 5, p. 62) : the beds have been quarried back to a large joint- 

 face, and the bedding-planes are consequently inconspicuous ; but 

 the direction of the bedding in each series is approximately indicated 

 by the trend of the chert-bands. This phenomenon seems to indi- 

 cate contemporaneous elevation and erosion, causing local uncon- 

 formity ; though it is possible that the discordance of the two sets 

 of beds may be due to local thrusting. Dr. Wheelton Hind & 

 Mr. .J. T. Stobbs have described ^ a similar phenomenon in the 

 upper beds of the Carboniferous Limestone, seen in Waenbrodlas 

 Quarry, Halkyn Mountain (Flintshire). 



YII. COMPARISOX OF THE FaUNAL SfCCESSIOX IX THE MiDLAND 



Area with that in other Areas. 



(A) Correlation of the Carboniferous Limestone of the 

 Midland Area with the Dibunophylimn-Zonie of the 

 South-Western Province.' 



Di = Subzone of Dibunophyllum 6. 



This subzone may be correlated with the Lower Dibunoj>7ii/Uum- 

 Zone (DJ of the South-Western Province, the correlation being based 

 on the following characters common to the two developments : — 



(1) The occurrence of Dihunophyila of simple type. 



(2) The common occuri'ence of Daviesidla afif. comoides, 



(3) The absence of Cyathophyllum regium, Lonsdalia, and specialized 



Ciisiophyllids. 



D of the Midland area is much less richly fossiliferous than the 

 corresponding subzone of the South-^Yestern Province. Corals 

 such as Cyatliopliyllurii Murchisoni and Carcinoplujllum 0, charac- 

 teristically abundant in the South-AYestern sequence, are absent or 

 very rare in the Midlands. Productus hemispliericus abounds in D^ 

 of the South-^Yestern Province, but is distinctly uncommon in D^ of 

 the Midland area. 



1 Geol. Mag. n. s. dec. v, vol. iii (1906) p. 396 & pi. xxii. 



- On tbe Carboniferous Limestone of the South-Western Province, see 

 A. Vaughan, ' The Palseontological Sequence in tbe Carboniferous Limestone 

 of .the Bristol Area' Quart. Journ. Geol. Soc. vol. Ixi (1905) pp. 181 et seqq. ; 

 and ' The Carboniferous Limestone Series (Avonian) of the Avon Gorge ' Proc. 

 Bristol Nat. Soc. ser. 4, vol. i, pt. ii (1906) pp. 74 et segq. Also T. F. Sibly, 

 ' On the Carboniferous Limestone (Avonian) of the Mendip Area (Somerset) ' 

 Quart. Journ. Geol. Soc. vol. Ixii (1906) pp. 324 et seqq. 



