190 CARBONIFEROUS. 



The thickness of the Lower and IMiddle Coal-measures is estimated 

 at about 1000 feet. The coal-seams vary from one to six feet in 

 thickness. Cannel Coal is rare. 



There appears to have been some denudation of the lower portion 

 of the Coal-measures before the uppermost strata were deposited.^ 

 And the Great Symon " Fault," according to Mr. Marcus W. T. 

 Scott, indicates the existence of an old valley or estuary of denu- 

 dation of the Coal- and Ironstone-measures, in which, subsequently, 

 other strata of the Coal-measures were deposited.^ 



The Pennystone Ironstone nodules found in the Lower Coal- 

 measures often yield, when split open, impressions of Ferns, fruits 

 of Lepidodendron, Insects, and Crustacea. The Crustacea belong 

 to the order Xiphosura, and the genus Prestwichia, named by Dr. 

 H. Woodward, is allied to the recent King-crabs. 



The Chance Pennystone is the highest bed of ironstone in the 

 series. In former years Coalbrookdale produced the best iron in 

 England. 



The Forest of Wyre (or Bewdley Forest) Coal-field is connected 

 with that of Bridgenorth by a band of Coal-measures stretching 

 through Billingsley ; and southwards the Coal-measures extend to 

 Bewdley and Abberley. The Coal-measures rest on the Old Red 

 Sandstone and are overlaid by Permian rocks.^ The coal-seams of 

 the Forest of Wyre are thin and of inferior quality, being charged 

 with much pyrites. The coal is, however, useful for lime- 

 burning, etc.* 



Outlying tracts of Coal-measures occur on the Titterstone and 

 Brown Clee Hills in Shropshire, and at Cleobury Mortimer. In 

 the former two cases the beds are capped by basalt, locally known 

 as Jewstone. In the Cornbrook Coal-field (Titterstone) the Coal- 

 measures are to a large extent covered with this igneous rock, 

 which has served to protect them from denudation. It varies in 

 thickness from 60 to 150 feet. In the Brown Clee Hills the Coal- 

 measures rest on the Millstone Grit and Lower Old Red Sand- 

 stone, while at Harcott there is a trace of Coal-measures resting 

 directly on the Old Red Sandstone.* 



Further south, between Malvern and May Hill, several exposures 

 of Coal-measures occur between the New and Old Red Sandstone. 

 In this tract, sometimes termed the " Newent Coal-basin," four 

 seams of coal were at one time worked at Bowlsden, near 

 Newent.^ 



^ D.Jones, G. Mag. 1S71, p. 200. 



2 Q. J. xvii. 463. 



3 Q. J. xxiii. 32. 



* G. E. Roberts, The Rocks of Worcestershire, p. 130. 



* See Murchison, Silurian System, p. 113; D. Jones, G. Mag. 1871, p. 363, 

 1873, p. 350. 



•^ Murchison, Proc. G. S. ii. 121 ; J. Phillips, Mem. Geol. Suivey, vol. ii. part i. 

 pp. 104, 15S. 



