Geology of Coalbrook Dale. 445 



A few feet above the " Wliite flat", in the northern division, is the " Blue flat" ironstone. 

 The large, mis-shapen nodules of this measure are full of casts of Unios, and vegetable impres- 

 sions of the order Lycopodiaceae, well preserved but in great confusion. 



A thin seam of clay separates that ironstone from the " yard-coal ", upon which reposes the 

 "yellow flat" ironstone, containing a few Unios, and several species of Sigillaria, Calamites, and 

 many genera of Lycopodiaceae. 



The strata, between that bed and the " Top coal," contain organic remains analogous to those 

 of the last three or four beds. The bass above the "Top coal" contains, in Donnington, remains 

 of the Megalichthys, Gyracanthus, and other fishes, with a few Unios. It is only in the north of 

 the coal-field that the hailstone measure is known ; the nodules of which are large, and the bed 

 is remarkable for the abundance and beauty of its vegetable reliquiae. The Cyclopteris orbi- 

 cularis, and several other species of the same genus characterize this deposit. They are always 

 beautifully preserved, every fibre being perfect ; and the thin, delicate tissue of the plant is 

 indicated by the sharp and unbroken, though crumpled state of the leaf. This bed is also distin- 

 guished by the presence of Lycopodiaceae, Asterophyllites, and Bechera. I discovered no ani- 

 mal remains in it. It is remarkable that, although the vegetable Impressions are so abundant in 

 the ironstone nodules, yet none are found in the shale in which the ironstone is Imbedded. This 

 is also the case, in a great degree, with all the fossils of the other ironstone strata. 



The thick bed of sandstone which overlies the " ballstone " at Ketley contains only a few vege- 

 table remains, the most common being casts of Calamites. 



For several yards above this sandstone, the strata inclose very few fossils, and they are chiefly 

 vegetable. 



The " Brick measure ironstone" is as much characterized by the paucity of organic remains, as 

 the other ironstones are by their abundance. I found only three small and imperfect impressions 

 of monocotyledonous plants. 



Ten or twelve yards higher Is the " Blackstone" measure. This ironstone contains a few casts 

 of Unios and Lycopodiaceae ; and I have found a few specimens of Orbicula rejlexa In the dark 

 shale of this stratum ; and, latterly, in Donnington Wood, some beautifully preserved small Lin- 

 gulae, together with remains of fishes. 



I am not aware tliat the strata between the " Blackstone" and " Chance Penneystone" are cha- 

 racterized by any particular fossils. The few which are met with, are Imperfect impressions of 

 Ferns, and other plants. 



The " Chance Penneystone," which Is the highest bed of Ironstone In the coal-field, is a deposit 

 of considerable interest. After the great preponderance of vegetables and Unios In the strata, be- 

 tween the Main Penneystone and this, we suddenly arrive at a deposit containing, in great abun- 

 dance, Leptcena scabricula, a fossil found only in the two Penney ironstones In this coal-field. 

 In some places it occurs in great abundance, one or more of these shells having served as a 

 nucleus for almost every nodule of ironstone, to the exclusion of any other fossil which I could 

 discover. This stratum is also characterised by the presence of the Hybodus, Megalichthys 

 Hibberti, Gyracanthus formosus, and Conularlae, presenting a remarkable analogy to the Penney- 

 stone as existing further southward, and which is 200 feet lower in the series. So great is the 

 resemblance, both in organic remains and llthological character, that it would be almost impos- 

 sible for any observer to distinguish between the two strata by an examination of the heaps at 

 the pit's mouth ; but the Chance Penneystone is not persistent ; and I am not aware of Its exist- 

 ence further to the south than New Hadley and part of Ketley. As it disappears, the Penney- 

 stone becomes richer in organic remains. 



To the " Chance Penneystone " succeed several thick strata of sandstone, with a few subordinate 



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