1865.] DAWSON — COAL-FOHMATION. 125 



The lower bituminous limestone contains Naiadites ovalis, ft. in. 

 Cythere, and scales of Lepidoid fishes. The lower coal has 

 much Cyperites and bark of 8igillaria, also bast tissue in 

 mineral charcoal. 



(Thick beds of grey sandstone and grey shale, with 

 drifted trunks of Badoxydon, Sigillaria, and Ca- 

 lamites, and leaves of Cordaites) 532 



( Grey shale. 

 Coal-group 8 ... J. Coa^^inch ^ 



[ Argillo-arenaceous underclay, Stigmaria. 



This coal is laminated, the laminae being bark of Sigil- 

 larice. The underclay is very rich in Stigmaria. 



(G-rey sandstone with grey and red shale. Many 

 drifted trunks of BigiUaria and Calamites, and an 

 erect Sigillaria in the lowest bed of sandstone)... 1224 



{Grey shale. 

 Coaly matter and carbonaceous shale 2 

 Argillo-arenaceous vmderclay, Btigmaria, and iron- 

 stone. 



(Grey and red sandstone and shale and calcareous 

 bands, some of them bituminous. Near the 

 middle a thick band of laminated black shale with 

 Naiadites Icevis, Cyjjerites, and Lepidostrohis. 

 Drifted Calamites in the sandstones) 496 4 



Total thickness, according to Logan 3240 9 



g. Division 7. — This division consists principally of red and choco- 

 late, shales with red and grey sandstone, arenaceous conglomerates, 

 and thin beds of concretionary limestone. It may be regarded as the 

 base of the Millstone-grit formation. Its thickness is stated by Sir 

 W. E. Logan at 650 feet. 



No fossils, other than carbonized fragments of plants, have been 

 found in this division. 



h. Division 8. — This division consists of reddish shales with green- 

 ish and red sandstone, grey shale, grey compact limestone, and gyp- 

 sum. It may be regarded as the upper part of the Lower Carboniferous 

 formation ; and almost immediately under its lowest beds there are 

 marine limestones with Procluctus cora and other characteristic Lower 

 Carboniferous fossils. 



Only fragments of plants, often replaced by sulphuret of copper, 

 have been found in this division. Its thickness is stated by Logan 

 at 1658 feet. 



§ lY. EeMAEKS ON THE AnIMALS AND PlANTS WHOSE EeMAINS OCCUR 



IN THE Coil. 



1. Introduction. — Under this heading I shall, in the first place, 

 present a tabular view of the relative frequency of occurrence of the 

 several genera in the beds of coal and their roof-shales, without 

 reckoning the almost invariable occurrence of Sligmaria in the under- 

 clays, which is of course to be taken as an indication of the existence 

 of Sigillarioid trees in connexion with the growth of the coal. 



