544 MB. T. C. OANTRILL ON SPIRORB1S-LIMESTONE, ETC., [Aug. 1895, 



limestone so clearly associated with red rocks is very suggestive of 

 the ' continental ' rather than marine habitat of Spirorbis pusillus. 



If it be granted that the red colouration is original, it can only 

 be the reflection of external changes in the conditions of deposit. 

 We have here, then, a strong character which allies the beds under 

 discussion with the whole of the true Permian and Trias. 



(3) Analogies from other Districts. 



It has of late years been strongly urged by several observers that 

 colour must be regarded as of little importance in deciding the 

 affinities of beds. Hence series of red strata formerly considered as 

 ' Permian ' have in several districts been entirely relegated to the 

 underlying Coal Measures, on the evidence of the presence of Coal- 

 Measure fossils, or of seams of coal or Sjrirorbis-limestone, or the 

 absence of any marked break at the base of the red series. 



Thus the red clays of Walsall Wood and Essington in South 

 Staffordshire, at first regarded as Triassic, then ' Permian,' were 

 subsequently regarded by Jukes as Coal Measures. 1 



We have seen that the ' Permians ' of Hamstead have been 

 shown by the fossil flora to be of Upper Coal Measure age. Again 

 Mr. W. T. Aveline 2 points out that the Lower Eed Sandstone of 

 Sedgwick (Rothliegende of Murchison), with its coal-plants and coal- 

 beds, has generally proved to be Coal Measures or Millstone Grit, 

 ' and the Permians of Staffordshire and Warwickshire are now said 

 to be Upper Coal Measures of a red colour,' although he gives no 

 evidence in support of the statement And again, the same 

 observer, as pointed out by the Pev. A. Irving, 3 after a re-survey of 

 the southern end of the Derby and Nottingham. Coalfield, gives up 

 to the Coal Measures the red sandstones and shales which lie con- 

 formably on the Coal Measures, and which were formerly regarded 

 as Lower Eed Sandstone, i. e. ' Permian.' The reason for the change 

 seems to be that there is a greater break above than below the 

 doubtful beds. 



The Eotherham, Ackworth and Pontefract Ped Pocks, first 

 regarded as Coal Measures, then ' Permian,' are now considered to be 

 Coal Measures. 



The Plumpton Pocks and Knaresborough Grits are now regarded 

 as Millstone Grit, 4 and not ' Permian,' as was at first supposed. 



Moreover, there are other masses of red rocks which have long 

 been considered Upper Coal Measures, and which apparently 

 resemble the Lower Sandstones and Marls of the Wyre Forest 

 district in containing Sjrirorbis-limestones and thin coals, and in 



1 ' South Staffordshire Coalfield,' 2nd eel. Mem. Geol. Surv. 1859, pp. x. & 102. 



2 Geol. Mag. 1877, p. 156. 



3 Ibid. 1882, p. 221.: 



4 J. Clifton Ward, Quart. Journ. Geol. Soc. vol. xxv. (1869) pp. 291-297. 



