1865.] . DA.WSOIC- — COAL-FORMATION. Ill 



corresponds to the lower part of the Middle Coal-formation, and 

 probably to the Lower Coal-formation of some American authors. 

 Its thickness, according to the measurements of Sir WiUiam E. Logan, 

 is 2539 feet. It is remarkable for the prevalence of grey sandstones 

 and grey and dark-coloured shales. It constitutes the part of the 

 section re-examined by Sir C. Lyell and myself in 1852 ; and in the 

 memoir which I subsequently published it is divided into 27 groups 

 or subdivisions. For faciUty of reference these groups are indicated 

 by the Roman numerals in the following pages, beginning with the 

 highest group, xxvii. 



XXVII. 



C Bituminous limestone and calcareo-bituminous shale ^^' 



I 4 feet 



Co^l-groui^ I -icoall foot : 5 



i Grey argillo-arenaceous underclay, Stigmaria. 



The roof has Naiadites carbonarius and JS^. elongatus, Spi- 

 rorbis (urbonarius, scales of Ithizodus, and obscure vege- 

 table fragments. The coal contains flattened JSigillarice, 

 Cordaites, Alethojpteris lonchitica, Gyperites, Calamites Nova- 

 scotica, and many vascular bundles of ferns. 



(Grey sandstone and shale with six under clays and 

 erect Sigillaria at two levels; also a thin shale 

 with Naiadites, Cythere, Calamites, and Cordaites. 

 One of the sandstones has scales and teeth of a 

 large fish (? Bhizodus) and plants covered with 



Spirorhis) 50 



/Grey argillaceous shale. 

 Coal 1 inch. 

 Clay 3 inches. 

 Coal 1 inch. 

 Coal-group 2 . . . -{ Clay 1 inch. 

 Coal 1 inch. 

 Shale 4 inches. 



Coa? 3 inches 1 2 



^ Grey argillo-arenaceous imderclay, 8tigmaria. 



The roof has numerous vegetable fragments and flat- 

 tened Sigillarice and Calamites. One of the coals contains 

 mineral charcoal, showing bast tissue, scalariform tissue, 

 and fragments of epidermis. The lower coal has bark of 

 Sigillaria, Stigmaria, and Cyperites, also numerous Trigo- 

 nocarpa and vascular bundles of ferns. The clay partings 

 and the underclay have obscure rootlets, probably of Stig- 

 maria. 



(Arenaceous underclay and shale with remains of 

 Stigmaria.) 



{Grey argillaceous shale. 

 Coal^inches 3 

 Hard argillo-arenaceous underclay, Stigmaria. 



The roof has stumps of Sigillarice, erect and with roots 

 of Stigmaria descending among them from the bed above. 

 The coal, which is coarse and earthy, has vascular bundles 

 of ferns, scalariform vessels, bast tissue, and scales and 



