186 THE CARBONIFEROUS SYSTEM. 



During the greater part of the time occupied in the formation of these 

 beds, the locality must have been a sandy or muddy sea-bottom, 

 receiving much mechanical detritus, or an expanse of flats of reddish 

 mud and brown or gray sand, covered by the tides. There are, how- 

 ever, some evidences of terrestrial conditions. In the lowest beds is 

 a large erect stump, filled with laminated clay after the complete decay 

 of its wood. In the clay filling it were abundance of fern leaves, 

 Cordaites, Lepidophylla, a few plants with attached Spirorbis, and a 

 shell of Naiadites. This tree was rooted in a thick underclay full of 

 rootlets of Stigmaria. Higher up there are several thin coaly bands, 

 with underclays ; many of the shales abound in leaves of Ferns and 

 Cordaites, probably drifted, and the highest sandstone showed a large 

 erect tree. 



Subdivision XI. commences with a soil resting immediately on the 

 truncated top of the tree last mentioned. On this soil was formed a 

 deep swamp, now represented by three feet of coal and bituminous 

 shale in alternate bands. Large quantities of clay and sand buried 

 this swamp, but not in such a manner as to preclude the growth of 

 trees, many of. which were entombed in the erect position. In these 

 sandstones and shales, no less than six erect trees were observed at 

 different levels, the lowest being rooted in the shale forming the coal- 

 roof; fifteen feet of the trunk of one of these trees still remain; two 

 others were respectively five and six feet high. Erect Calamites were 

 also observed. The soil which was formed on the surface of these 

 beds supports one of the thickest coal-beds in the section, marking a 

 long and undisturbed accumulation of vegetable matter; and after the 

 deposition of 18 feet of underclay and shales, there is another equally 

 thick though coarser bed. We have here, as in some previous groups, 

 three distinct conditions of the surface: — first, terrestrial surfaces 

 more. or less permanent; secondly, undisturbed marine or brackish 

 water conditions ; thirdly, intervening between these the deposition, 

 probably with considerable rapidity, of sandy and muddy sediment. 

 We may also observe that, admitting the Stigmaria to be roots of 

 trees, there are five distinct forest soils without any remains of the 

 trees, except their roots; and we shall find throughout the section 

 that the forest soils are much more frequently preserved than the 

 forests themselves. 



In the large series of beds included in Subdivisions XII. and XIII., 

 there are no less than thirteen distinct forest surfaces marked by 

 underclays or erect trees, and at least five periods of submergence 

 indicated by mussel-beds, and three of them, at least, of very long 

 duration. It will be observed that, in several instances, the order of 



