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Notices of Memoirs — G. S. Morton. 



Cefx-t-Fedw 



Sandstone. 



Tabular View of the Carboniferous Limestone and Cefn-y-Fedw Sand 



STONE IN THE CoUNTY AROUND LlANGOLLEN. 



Feet. Upper 



'Aqueduct Grit, or Upper Sandstone and) »„ ") Cefn-y-Fedw, 



Conglomerate j )> Dee Bridge, or 



Upper Shale 30 | Millstone-grit 



Dee Bridge Sandstone 30 J Series. 



Lower Sliale with Fire-clay and bands \ , „ ~1 



of Limestone ) | 



Middle Sandstone 200 ! 



Cherty Shale 50 T 



Lower Sandstone and Conglomerate 250 j 



l_ Sandy Limestone 75 J 



Upper Grey Limestone 300 ) Upper Carboni- 



,, White ,, 300 ( ferous Limestone 



Lower „ ,, 120 ) 



„ Brown „ 480 / 



1923 



Carboniferous 

 Limestone. 



Middle and Lower 



Cefn-y-Fedw, 



or 



Yoredale 

 Series. 



Lower ditto. 



Upper Old Red Sandstone 300 feet. 



Each of the subdivisions was separately described, and a section 

 from the Ty-nant ravine to Tyfyn-uchaf was exhibited, showing the 

 regular succession of the whole of the sti-ata from the Old Red Sand- 

 stone to the Coal-measures. The following table shows the gradual 

 attenuation of the Carboniferous Limestone towards the south-east. 



Subdivisions. 



Ty-nant. 



Tan-y- Trevor 

 Castell. Rocks. 



Bronheulog-. Fron. 



Upper Grey Limestone 



300 

 300 

 120 



480 



300 

 250 

 115 

 360 



250 

 140 

 117 



loot 



66* 

 99 

 104 



26 1 



88* 



,, White „ 



27t 







,, Brown ,, 











1200 : 1025 



607 



295 



115 



* Upper portion has been denuded. 



t Reposes on the Weulock Shale. 



X Lowest beds not ascertained with certainty. 



This section shows how the limestone diminishes in thickness 

 Avith the rise of the Wenlock Shale towards the south-east. Between 

 the Ty-nant ravine and Fron, four miles from the former place, the 

 attenuation is not less than 900 feet. 



The list of fossils collected by the author contained seventy-seven 

 species. Of these fifty-eight occur in the Upper Grey Limestone, 

 and only eighteen in the Lower Brown Limestone. If the Carboni- 

 ferous Limestone is simply divided into Upper and Lower Limestone, 

 thirty-eight species are peculiar to the two upper subdivisions, and 

 nineteen to the two lower subdivisions ; twenty species being com- 

 mon to both. However, the species are by no means confined to the 

 subdivisions in which they are found near Llangollen, for they 

 occur at different horizons in other districts. 



