﻿Vol. 64.] CA.EBONIFEROUS LIMESTONE 01' THE MIDLAND AKEA. 57 



So far as I am aware, no extensive development of chert 

 occurs anywhere below I).,. By its restriction to D., and Dg, 

 therefore, the presence of an extensive series of cherty beds con- 

 stitutes a feature of stratigraphieal value. Beyond this, however, 

 the presence of chert cannot be said to have any significance as an 

 indication of horizon, except within very limited areas. 



The changes of lithological facies which take place in various 

 portions of the sequence, and especially in this subzone, will 

 probably be found, in the light of further investigation, to be 

 of importance in their relation to faunal facies. In this connexion 

 it may be mentioned here that the abnormal faunal facies of the 

 Lonsdalta-subzone presented by the ■■ brachiopod-beds ' (see above, 

 p. 49) is associated with a distinctive lithological facies : namely, 

 a conspicuous development of pure, white limestones. 



V. Description or certain Sections of the Cvathaxonia- 

 Spbzone : Relation of the Cyathaxoxia-^x^'bzoi!^!^ to the 

 Pendleside Series. 



The Ci/atha.vonia-s\ihzone varies considerably in diflPerent parts of 

 the area, both as regards its thickness and as regards the abundance 

 of its fauna. Where the subzone attains a considerable thickness, 

 the fauna is, as a rule, proportionately well developed. It has 

 already been stated that this subzone includes the highest beds o^ 

 the Carboniferous Limestone, succeeding the Lonsdalia-suhzone, and 

 also the passage-beds between the Carboniferous Limestone and the 

 Pendleside Shales, wherever such passage-beds are developed, I 

 have not discovered any section in the Midland area that exhibits 

 a complete sequence, from the uppermost part of the Carboniferous 

 Limestone, through a well-developed series of passage-beds, up into 

 the Pendleside Shales. Numerous good sections of D.^ are to be 

 found, but the majority of these are confined either to the topmost 

 beds of the Limestone, or to the passage-beds between the latter 

 and the true Pendleside Shales ; and such exposures of an unfaulted 

 junction of the Carboniferous Limestone and the Pendleside Series 

 as do exist, occur in localities where the change from one division 

 to the other is sharp. 



In order to give some idea of the varying development of the 

 subzone and its relation to the Pendleside Series, I append the 

 following notes on the more important sections examined by me. 

 Among the sections here described, the most instructive are those 

 of Longstone, Matlock Bath and Cromford, Tissington, JSTewton 

 Grange, and Manor Farm near Wetton. 



(A) Sections in the Eastern Part of the Area. 



(i) Longstone. 



In the typical section, the railway-cutting immediately east of 

 Headstone Tunnel, west of Longstone Station, gives an excellent 



