178 THE CARBONIFEROUS SYSTEM. 



This coal is laminated, the laminae being bark of Sigillarice. 

 The underclay is very rich in Stigmaria. 



(Gray sandstone with gray and red shale. Many ft. in. 

 drifted trunks of Sigillaria and Calamites, and an 

 erect SigiUaria in the lowest bed of sandstone) 1224 

 r Gray shale. 

 C al oTonn Q J ^'^^t'> matter and carbonaceous shale . . .02 



'° " I Argillo-arenaceous underclay, Stigmaria, and iron- 

 ic stone. 



(Gray and red sandstone and shale and calcareous 

 bands, some of them bituminous. Near the middle 

 a thick band of laminated black shale with Naia- 

 dites Icevis, Cyperites, and Lepidostrohus. Drifted 

 Calamites in the sandstones) .... 496 4 



Total thickness, according to Logan 3240 9 



Division 7. 



This division consists principally of red and chocolate shales with 

 red and gray 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. 



Division 8. 



This division consists of reddish shales with greenish and red sand- 

 stone, gray shale, gray compact limestone, and gypsum. It may be 

 regarded as the upper part of the Lower Carboniferous formation ; 

 and almost immediately under its lowest beds there are marine lime- 

 stones with Productus cora and other characteristic Lower Carbon- 

 iferous 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. 



The number of coals reckoned may vary according to the manner 

 in which the several layers are grouped ; but as arranged in the 

 above sectional list, it amounts to eighty-one in all. Of these, 23 are 

 found in Division 3 of Logan's section, being the upper member of 

 the Middle Coal Formation ; 49 are found in Division 4 of Logan's 

 section, being the lower member of the ISIiddle Coal Formation ; 9 

 occur in Division 6 of Logan's section, or in the equivalent of the 

 Millstone-grit. 



