482 LUDLOW FORMATION, INCLUDING AYMESTRY (SEDGELEY) LIMESTONE. 



same dull indigo grey, argillaceous limestone as that which usually occurs in the centre 

 of the Ludlow formation of Salop, though it is not quite so crystalline as at Aymestry. 

 This limestone not only contains the Lingula Lewisii and the Terehratula Wilsoni, fossils 

 which characterize it over wide spaces, but also that remarkable shell the large Pen- 

 tamerus Knightii, which is almost peculiar to this zone. The disappearance of this fossil 

 at many intermediate places 1 where the rock is less calcareous, and its re-appearance at 

 so distant a point as Sedgeley, where calcareous matter is again abundant, is one of 

 the best proofs that geological inquiry has established of the re-appearance of large 

 testacea where lime is present, and their disappearance where it thins out. Now, as we 

 find the other and smaller testacea, which are the congeners of these Pentameri, at Ay- 

 mestry, in situations where there is no lime (so invariably, indeed, that throughout a 

 continuous extent of upwards of 100 miles I have, by their presence alone, been enabled 

 to mark the position of the limestone), we are led to infer that the animal inhabiting the 

 thick shell of the Pentamerus, could only exist in those bays of the ancient sea in which 

 much calcareous matter prevailed. 



This limestone of Sedgeley is distinguished from that of Dudley, not only by organic remains and 

 lithological structure, but also by burning to a dark- coloured lime, (hence the name of black lime- 

 stone) which is of value for the same economical purposes as the limestone near Ludlow, in making 

 most durable stucco and mortar, particularly under water ; but if used in agriculture its application 

 must be limited to the light lands, which it enriches by its argillaceous as well as calcareous in- 

 gredients. 



The limestone of Sedgeley is separated from that of Dudley, by a considerable thickness of shale 

 (the equivalent of the Lower Ludlow rock), which occupies the eastern and south-eastern slopes of 

 the Beacon hill, but owing to the rounded forms of the hills the strata are not well exposed, and 

 their mineral poverty has never led to their being uncovered. The same "mudstone" strata oc- 

 cupy the rising grounds between the Wenlock limestone of Cinder Hill, and the outcrop of the coal, 

 which is exposed on their slopes in the Rookery Lane. 



"Turner's Hill." — The Ludlow rocks occupy this small oval hill, lying between Lower Gornals 

 and the Streights. They are surrounded, as at Sedgeley, by thin or slightly productive coal mea- 

 sures, of which a very narrow band, not exceeding two or three hundred paces in width, separates 

 them on the west from the Lower New Red Sandstone of the Himley district, whilst to the east and 

 south they throw off the unproductive carboniferous sandstone of Gornals, in the manner expressed 

 in the section, PI. 37. f. 2. 



The only well-exposed beds are on the western face of the hill, where they consist of impure ar- 

 gillaceous limestone in small concretions, resembling the refuse beds of Sedgeley, in which the Te- 

 rehratula Wilsoni, Pleurotomaria, &c. are the prevalent fossils: the overlying beds of flaglike, dirty 

 yellowish sandstone contain a few casts of common Ludlow fossils. 



" The Hayes"— The ridge which rises at the Hayes, two miles west of Stourbridge, and is not 

 more than 300 paces in length and 1Q0 in width, very clearly belongs to "Ludlow rocks." Ex- 

 tending from north to south the strata dip from 40° to 50° to the east beneath the adjacent coal 



» The intermediate places are the Abberley and Malvern Hills, the valleys of Woolhope, Usk, &c. 



