IRONSTONE FORMATION OF THE FOREST OF DEAN. 225 



near Blakcney Hill, a little to the east of Staple Edge enclosure ; it 

 re-appears at Eed Hill, near Sydney. The effect of this fault, which, is 

 marked by a line of springs, has been this — the Coal-measures and Mill- 

 stone-grit cover and repose conformably on the beds below the Old Eed. 



The whole of the limestone-formation may be locally divided as fol- 

 lows, in descending order : — 



1. The ^'whitehead limestone" and calcareo- arenaceous red and purple- 

 coloured shales, graduating into the lowermost beds of Millstone-grit, 

 or the equivalent of that rock, one bed being slightly oolitic, near St. 

 Briavils, and at Coleford. Average thickness, 40 yards. 



2. Grey iron-stone formation. Grey and red-limestone beds. Thick- 

 ness, about 42 yards. 



3. Black-rock" limestone, calcareo-argillaceous shales, and '^"Fore- 

 line" limestone, often called the " Mountain-limestone," graduating into 

 the uppermost beds of Old Eed; average thickness, probably, 15 yards, 

 but very variable. 



The middle and lower divisions are moderately fossiliferous, but I am 

 not aware of any organic remains having been discovered in the beds 

 above the " Ironstone- formation," although, on Deans Meend, near 

 Mitcheldean, I have observed a thin bed of purplish arenaceous 

 limestone, on the upper surface of which there are certain ring and 

 pipe-like markings, which may probably be considered annelidal, or 

 made by marine worms. In a bed near the bottom of the " Grey beds" 

 some fine specimens of ''fish palates" have been found, and in the 

 Eed beds" some entrochites of large size. These grey and red beds 

 are highly crystalline, and average from two feet to a yard thick. The 

 innumerable small joints, however, by which they are traversed, render 

 the stone valueless for building-purposes, although it is most extensively 

 quarried for the supply of the iron-furnaces, as well as for burning into 

 lime. 



But the real harvest for the palaeontologist is to be gained in the 

 carboniferous shale-partings or ancient mud-beds, which are inter- 

 stratified with the thin beds of limestone and calcareo-arenaceous 

 shales that form the transition to the Devonian beds. The series which, 

 in all probability, represents the carboniferous shales of Devonshire is 

 a perfect charnel-house of encrinital remains ; and I know of no better 

 spot for the collector than the section, or, in quarry-language, ''loose 

 end," which is obtained in an old quarry near the summit of Plump 



