C— GEOLOGY. 85 



in the Bristol district, Midlands and North Wales at a lower level (D.^) than 

 the proposed zone is no valid argument against its adoption. 



There is, I think, no difference of opinion as to the limits of Di ; it begins 

 with the entry of the D-coral fauna, and particularly of Cyathophyllum 

 {PalcBOsmilia) murchisoni, and ends below the Girvanella bed. 



The following classification of the chief limestones of the North of 

 England is drawn up with the aid of Dr. S. Smith. 



Di, the sub-zone of Cyathophyllum murchisoni. — The base of D is marked 

 by the entry of the D-coral fauna. Dp which in Westmorland has at 

 the base a well-known level, the Bryozoa bed of Garwood, includes 

 part of the Great Scar limestone of Yorkshire, part of the Melmerby 

 Scar limestone series of the North- West Pennines, and all the strata from 

 the Redesdale and Woodend limestones at the base to the Oxford lime- 

 stone at the top in Northumberland. In West Cumberland it includes 

 the sixth and fifth limestones, and the lower part of the fourth up to the 

 base of the Girvanella nodular bed. 



Dj, the Lonsdaleia sub-zone of Vaughan's original classification, is 

 divided into lower D.^, the sub-zone of Lonsdaleia floriformis (lower 

 Lonsdaleia beds) ; upper D.,, the sub-zone of Lonsdaleia duplicata (upper 

 Lonsdaleia beds). The Girvanella nodular bed, which is very well marked 

 throughout much of Yorkshire and the North-west Province, is found also 

 in Northumberland (Oxford limestone), and forms an admirable datum 

 line for the base of D.^. The top of D.^ will lie just below the Orionastrcea 

 level, and in D.^ will be included all strata from the Productus giganteus 

 to the Productus edelbergensis beds of the Settle district, the Gayle, 

 Hardraw, and lower part of the Simonstone levels of the Dale country, 

 and in Northumberland from the level of the Oxford limestone to that 

 of the Eelwell and Tynebottom limestones. 



The Yoredalian under the scheme here adopted includes the Orion- 

 astrcea zone and others not yet defined of the Southampton report, and 

 extends on to the base of the Lancastrian. In the Settle area it includes 

 the strata from the Orionastrcea level (Simonstone) to the Great, Upper 

 Scar, or Main limestone, and in the Dale covmtry also strata above the 

 Main limestone. In the Alston district and in South Northumberland it 

 includes the succession from the Tynebottom to the Fell Top limestone. 

 As has been already pointed out, some of these strata may prove to be of 

 the age of the lower Lancastrian. 



The Shaly development {Goniatite or Culm phase P). 



Rocks of this phase form the large Culm area of North Devon, and in 

 the North much of the contiguous parts of Yorkshire, Lancashire, and 

 Derbyshire, the type area beiiig that of Pendle Hill and Clitheroe. 



Although Wheelton Hind devoted much time to their study, they 

 were, until a comparatively few years ago, relatively neglected by workers 

 on the British Carboniferous rocks, but, thanks primarily to Mr. W. S. 

 Bisat's work on the goniatites, this is far from being the case at the 

 present time, and their succession is now known with an accuracy and 

 detail which has often not yet been reached in areas where the rocks are 

 of the calcareous phase. Mr. Bisat's work on the goniatites, following on 



