﻿Vol. 64.] CARBONIFEROUS LIMESTONE OF THE MIDLAND AREA. 67 



Midland area. It is unfortunate that the base of the Carboniferous 

 Limestone is not exposed in the Midland area ; for, in view of the 

 relative geographical position of the Midland and North-Wales areas, 

 and the general similarity of their facies, there is some reason to 

 expect that the base of the Carboniferous Limestone occurs at 

 approximately the same horizon in both areas. A knowledge of the 

 horizon of the base of the Carboniferous Limestone in the Midland 

 area would afford valuable evidence in an important branch of 

 Carboniferous physiography. 



The relation between the faunal succession in the two areas may 

 be summarized as follows : — D^ of ]^}"orth Wales presents a more 

 normal character, compared with the South-Western Province, than 

 D^ of the Midland area. This is exemplified by the abundance 

 of Cyatliophyllum MurcJiisoni and Productus hemispliericus in the 

 J^orth-Wales development. 



It is in the characters of the faunal assemblage of D^ that the 

 two areas are most closely linked. Both areas exhibit a charac- 

 teristic D^ coral-fauna, and the differences are unimportant, as 

 compared with the points of identity ; while the ISTorth-Wales area 

 possesses a rich brachiopod-fauna, practically identical with that of 

 the Midland area. 



In the development of Dg there is a considerable difference 

 between the two areas. The Midland succession includes a well- 

 developed Cyatlmcconia-s\xh7.onei, which possesses a coral-fauna essen- 

 tially distinct from that of the iojis cZaZia-subzone, Cyatliaooonia and 

 various Zaphrentids being abundant, while Lonsdalia Jloriformis 

 is absent. The Gyathacconia-fsLiinai attains a fine development in 

 the passage-beds between the Carboniferous Limestone and the 

 Pendleside Shales, and the subzone often includes a considerable 

 thickness of the uppermost beds of the Carboniferous Limestone 

 proper. In the ISTorth- Wales succession, on the other hand, while 

 the D3 coral-fauna is partly developed in the uppermost portion 

 of D^, associated with Lonsdalia and other characteristic D^ corals ; 

 and, while Cyathaxonia and Amplexi-Zaphrentis do occur in 

 passage-beds at the top of the Carboniferous Limestone, there 

 is no development of a distinct Cyathaooonia-^uhzone at all nearly 

 equal to that of the Midland area. 



On the whole evidence, it may be concluded that the Carbo- 

 niferous Limestone of the Midland area and that of North Wales 

 belong to one Province, distinct from the South-Western Province. 

 The Dibunojohyllum-Zone of this Midland Province differs from 

 that of the South-Western Province in the richness of its brachiopod- 

 fauna, and the Midland Province is further distinguished by the 

 development of a CyatJiaxouia-sub'/.one at the top of the Dihuno- 

 j)hyllum-Zone. This Cyathaxonia-snhzone has its typical develop- 

 ment in Derbyshire and North Staffordshire, and is less clearly 

 developed in North Wales. 



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