TJie Carboniferous Succession beloic the Coal- Measures. 501 



firmly established, that is to say, the cherty deposits of North 

 Yorkshire at the top of the Yoredale Series, tlie cherts of the Sykes 

 in the Trough of Bolland, North Staifordshire, Derbysliire, the 

 rotten-stones of Glamorgan, and the cherts of Codden Hill, Devon- 

 shire, appear from pal^ontological evidence to be homotaxial and 

 contemporaneous. These cherts succeed beds with a Visean, or, to 

 be more precise, an Upper Dihunoplnjllnm fauna, and in every case 

 except that of North Yorkshire (near Leyburn) are succeeded by 

 the Posidonomya Becheri beds of the Pendleside Series. In North 

 Yorkshire it is known that P. Becheri beds are absent, this deposit 

 never having been found hitherto in such high latitudes. We do 

 not propose to discuss here the origin of the North Wales cherts. 

 It is sufficient for our purpose to say that the cherts themselves are 

 finely and regularly stratified, that the quantity of chert varies from 

 a high percentage to a small one, that the limestones below the 

 chert are largely impregnated with this mineral, and probably the 

 chert is a replacement mineral. 



At the inlier of Carboniferous Limestone at the Sykes in the 

 Trough of Bolland massive cherts, most closely resembling those of 

 North Wales, lie on the top of the upper beds of the Carboniferous 

 Limestone, and are succeeded by black shales of the Pendlesside 

 Series. We are not aware that a cherty deposit occurs to that extent 

 anywhere else in that district, but chert is present on the top of the 

 inlier at Withgill. A.t Pendle Hill the Pendleside Limestone 

 contains numerous strings and nodules of chert. These are of course 

 higher up in the series. At the Sykes the beds are remarkably 

 unfossiliferous, but we obtained sufficient evidence to demonstrate 

 that the limestones belong to the Upper Dibunophyllum zones. 



In North Derbyshire remains of a large deposit of chert are to be 

 seen near Pindale, east of Castleton, but on the western flank of the 

 Staffordshire-Derbyshire inlier chert is very irregular in its 

 occurrence. It is, however, present at Mixon below beds with 

 Posidonomya Becheri, and in beds, as strings and nodules, containing 

 Cyathaxonia and Amplexi-za-phrentis at Warslow, and as a cherty 

 limestone on the eastern flank of Thorpe Cloud. On the eastern 

 flank of the Pennines massive chert occurs at Bakewell at the top 

 of the Carboniferous Limestone and above the Cyathaxonia beds, in 

 which the black marble of Ashford occurs, this Black Limestone 

 probably being on the same horizon as the ' Aberdo ' Black Limestone 

 of North Wales. 



In South Wales the Black Limestones of Oystermouth Castle 

 contain Amplexi-zaphrentis, and are the representatives of the 

 Cyathaxonia zone in South Wales. These beds are in turn succeeded 

 by the rotten-stone beds of Bishopton, evidently decomposed cherts, 

 the equivalents of the Flintshire cherts. 



At Bishopton the rotten-stones are succeeded by a black shale 

 series which has a limited but definite Pendleside fauna, Posidoniella 

 Icevis and Glyphioceras bilingue. 



[It is necessary to inquire as to what beds, if any, are the 

 representatives of the cherts in those parts of North Wales where 

 they do not occur. The question is one that can only be solved by 



