Geology of Coalbrook Dale. 441 



with fluviatile shells, and thus accumulated those strata, principally of sand- 

 stone, which are characterised peculiarly by terrestrial or fresh-water remains. 

 This subject will be discussed more fully in the conclusion ; and I proceed 

 to a particular account of the zoological and botanical reliquiae of the different 

 beds. (See also Appendix C, list of organic rema i s.) 



Upon the hard sandstone conglomerate, which forms the lowest stratum of tlie coal-measures, 

 reposes a seam of coal. See Diagram, PI. XXXVII. 



To this succeeds thin beds of sandstone and shale; and in one of the latter occurs, at Wimsey 

 Styches and Caughley pits, Madeley parish, the " new mine ironstone," which contains a very 

 ievi vegetable remains and Unios. 



A few yards higher is a series of sandstone strata, characterised by numerous casts and im- 

 pressions of the Stigmariajicoides; and it also contains Calamites and Sigillarise. About the 

 centre of these strata is a bed of whitish sandstone, with ironstone, called " the Crawstone," 

 which abounds with the remains of the Stigmaria Jicoidcs, some ten inches in diameter ; and, occa- 

 sionally, with casts of Unios, remarkable for their preservation and smooth surface*. Many of the 

 Stigmaria found at New Lawley, exhibit the central pith-tube structure beautifully preserved. It 

 was in a specimen from this locality that the singular anatomy of the plant was detected by Pro- 

 fessor Lindleyf. 



A few feet above the crawstone is the little-flint coal, the only seam which in any part of 

 the coal-field occurs between two strata of sandstone. A singular phenomenon is frequently pre- 

 sented by this bed. Having been informed that at Madeley, Broseley, and elsewhere, the coal 

 is occasionally so pebbly that it cannot be used, I inspected the bed, and 1 found that it was 

 traversed horizontally in all parts by small flattened tubes of white sandstone, proceeding from 

 stems of the Stigmaria jicoides, and imbedded in the coal. The length of these bodies, or casts 

 of leaves, I could not ascertain ; but it was evident, from the condition of the stem and from the 

 leaves being generally attached, that the plant could not have been much disturbed from its ori- 

 ginal position. The stems are generally horizontal, or gently inclined, and slightly flattened ; 

 and the leaves, which proceed from them at right angles, or nearly so, are very little com- 

 pressed between the laminae of the coal. The sandstone, which has replaced the stem, bark, and 

 leaves, is finely grained, and remarkably white. How to account for its infiltration into the body 

 of plants placed in a thick seam of coal offers an interesting inquiry J. In the roof of the 

 coal, impressions oi Stigmaria jicoides are common, with a few Calamites. 



To this coal succeed thick sandstones, with a few similar vegetable casts and impressions. 



In the thin beds of shale and clay separating the clod, randle, sill, and best coals, which overlie 

 the thick sandstones, the multitude of vegetable impressions is very surprising. They lie horizon- 

 tally, and in all directions. Amongst them are Poacites, Calamites, Lepidodendra, Sigillariae, and 

 a few Stigmaria ; but the characteristics are Sphenopteris, Neuropteris, and Sigillariae, some of 



* Hitherto found only at Madeley and Broseley. 



t Fossil Flora, Plate 1G6. 



X The entangled Stigmaria may have decayed subsequent to the partial consolidation of the 

 coal ; and through small crevices in the coal, or the narrow tubes of the long leaflets, the fine over- 

 lying sand may have been forced, by the gradually increasing superincumbent pressure ; the con- 

 tinuation of which would, by further compressing the stratum of coal, slightly flatten the imbedded 

 casts. 



