386 Dr. Wheelton Hind 8^ John T. Sfobbs— 



area some of the sections disclose the unconformity between 

 Carboniferons and Silurian rocks. An interesting outlier of 

 Carboniferous Limestone also occurs at Corwen. All the exposures 

 examined by us will be observed to lie in the counties of Salop, 

 Denbigh, and Flint, with the exception of the district of Llysvaen, 

 wliich is part of Carnarvon. 



Usually, the best facilities for collecting were afforded by the 

 numerous quarries which are being, or have been, worked for road 

 metal, iron manufacture, lime, cement, chert, or building stone. 



The natural exposures of Carboniferous Limestone forming the 

 picturesque contours of the hills are so completely covered with 

 lichen growth that the fossils are totally obscured, and thus for the 

 purposes of systematic collecting they are not nearly so helpful as 

 at first sight they might seem to promise. In the series of rooks 

 overlying the Carboniferous Limestone the exposures and quarries 

 are comparatively rare, and all those examined by us occur in the 

 tract of country to the north and east of Halkyn Mountain in the 

 county of Flint. At certain horizons the fossils were very abundant, 

 and were of diagnostic value. The Carboniferous sequence of this 

 district, worked out by the aid of palaeontological data, has been 

 a much simpler affair tlian was anticipated. It is not proposed in 

 this paper to do more than indicate the main lines along which this 

 interpretation has been developed ; there is yet an immense amount 

 of labour required in order to till in the intervening details. 



2. A Critical Account of Previous Gkological Rkskarch in the 

 Carboniferous Hocks of North Walks. 



Much attention, during many years, was devoted to the study 

 of the Carboniferous succession in North Wales by the late Geo. H. 

 Morton. His various publications extend over the period from 1869 

 to 1901, when a posthumous paper on "The Carboniferous Limestone 

 of Anglesey " was edited by his daughter. 



His work was all done on palasontological lines, but unfortunately 

 he did not recognise any method for the establishment of life zones 

 in the Carboniferous rocks of North Wales. Eventually he estab- 

 lished a subdivision of the series founded on the colour of the 

 limestones. One of us had the opportunity, some yeai's ago, of 

 examining the very carefully labelled fossils in his collection, the 

 majority of which are now in the Natural History Museum, Cromwell- 

 road, South Kensington. 



All Morton's papers contain elaborate lists of fossils, an examina- 

 tion of which demonstrates that he recognised the important fact 

 that certain beds in various localities had a similar fauna. 



His writings also make it very obvious that he had doubts as to 

 the correlation of the peculiar calcareous grits, which, in the south 

 of Flintshire, Llangollen, Sweeney, and Oswestry Racecourse, succeed 

 or replace the purer limestones. There is no doubt that, to some 

 extent, Morton had certain broad palaeontological evidence for his 

 subdivision of the thick limestone of North Wales into Upper Grey, 

 Middle White, and Lower Brown, but he did not emphasize the fact. 



