The Carboniferous Succession below the Coal-Meamres. 503 



the Cyathaxonia beds that we do in various localities in North 

 Staifordshire, Derbyshire, and Yorkshire, i.e. limestones and shales 

 with Posidonomya Becheri and Fteriiiopecten pajiyraceus succeed beds 

 with Cyalhaxonia fauna. Here, then, the cherts do not succeed the 

 Cydthivxonia liinestones. Apparently there is no unconformity. 

 The sections atTeilia, the hill above Prestatyn, and Lady McLaren's 

 Quarry opposite Nant Hall seem to point to the sequence being 

 perfectly normal. It must be admitted that the Posidonomya Becheri 

 limestones near Prestatyn are far less carbonaceous than beds with 

 a similar fauna which succeed the cherts further east, and that 

 P. Becheri itself is ranch rarer near Holywell than it is at Prestatyn. 



Three solutions, neither of which are absolutely satisfactory, offer 

 themselves to this question. One that the cherts near Holywell are 

 the homotaxial equivalents of the P. Jiecheri limestones. Another, 

 that the cherts have heeii (;ut out l)y an unconformity or some 

 result of earth nu)veinentB. 



In favour of the first view : The cherts and P. Becheri beds rest 

 evei'ywhere, apparently conformably, on the Cyathaxonia beds of 

 the Upper DibnnnphyUum zone. Where cherts are present the 

 Pendleside Series is characterised by black shaly limestones, which 

 always succeed them. That the limestones and chert beds are both 

 thin-bedded and the beds very finely stratified. That plant-remains 

 have been obtained from the base of the cherts. 



On the other hand, the typical Pendleside fauna has not been 

 obtained from the cherts, but the fauna they do contain indicates 

 a somewhat lower horizon. 



If the north flank of the hill be followed from Prestatyn eastwards 

 to Lady McLaren's Quarry the section given on p. 451 is seen. 

 These beds rest on Cyathaxonia limestones, which are exposed 

 a few yards further west. Continuing eastward along the hill, the 

 outcrop of the Posidonomya Becheri limestones is seen as far as 

 Top Nant Farm. East of this farm is a shallow pit, from which 

 similar limestones were obtained. Some 200 yards south of this pit 

 is another shallow excavation which shows chert debris, and in 

 such condition and quantity as to indicate the broken up bed of 

 chert. No junction is seen, but it would seem that a bed of chei't 

 may here overlie P. Becheri limestones. The general dip of the 

 beds is north-east, and this outcrop of chert is about 470 feet 

 above O.D. The next most easterly exposure of chert is a quarter 

 of a mile away in a dingle west of the road over the hill to 'I'eilia 

 and Gwaenysgor. This is in the 200 feet contour, and the beds are 

 dipping very highly and evidently near a fault. 



For the present, then, the precise reason for the absence of the 

 cherts immediately in succession of the Cyathaxonia beds is not 

 apparent, and it is possible that they are the homotaxial equivalents 

 of the Posidonomya Becheri limestones. 



The difficidty of correlation has been enhanced by the unfortunate 

 assumption that Black Limestones were all on the same horizon. 

 There are no less than three series of Black Limestones each with 

 a definite fauna: the Black Limestones of the Holywell shales and 



