1000 DR R, KIDSTON, MR T. C. CANTR1LL, AND MR B. E. L. DIXON. 



On p. 19 of the same paper, under the heading of "Upper Coal Measures," he 

 further states : — 



" These form almost the whole surface of the coalfield except the districts indi- 

 cated. They consist of yellow, buff, and orange sandstones, shales and marls, of 

 great similarity to the upper parts of the Halesowen Sandstones of South Stafford- 

 shire. They contain many thin pyritous coals and several poor ironstones. The two 

 most important and constant coals are the Brock Hall seam and the Main Sulphur 

 seam, between which lies the Spirorbis Limestone." 



Since these remarks were written, now twenty years ago, much has been done to 

 elucidate the geology of these so-called " Upper Coal Measures." When writing my 

 paper on the Fossil Flora of the Potteries Coal Field in 1891, I referred all the " Red 

 Measures " which lay above the Spirorbis limestone that occurs 12 yards above the 

 Bassey Mine ironstone to the Upper Coal Measures,* and these, I understand, are the 

 same series of rocks to which Mr Cantrill referred his " Upper Coal Measures" of 

 the Wyre Forest. 



It was only through subsequent study of the fossil plants of these so-called 

 Upper Coal Measures that it was seen that much of this series of rocks must be 

 regarded as passage-beds between the true Upper Coal Measures ( = Radstockian 

 Series) and the Middle Coal Measures ( = Westphalian Series), and for these the name 

 of Transition Series was proposed.! The lowest of the beds that were classed by 

 the Geological Survey as Permian, and referred by Mr Cantrill to the Upper Coal 

 Measures, have now been identified with the Keele Group, and belong to the true 

 Upper Coal Measures or Radstockian Series.]. 



When the name " Transition Series " was proposed for these passage-beds, the 

 occurrence of this series in the Potteries Coal Field was pointed out ; but up till that 

 time they had yielded very few fossil plants, and in the absence of this guidance I 

 failed to discover the important place they held in North Staffordshire, and selected 

 as my type areas for the Transition Series the Lower Pennant Rocks of the 

 South Wales Coal Field and the New Rock and Vobster Groups of the Somerset 

 Coal Field. 



It is, however, to Dr Walcot Gibson § that we are indebted for our intimate 

 knowledge of the Transition Series as developed in North Staffordshire, and of the 

 three groups of which it is composed. These are, in descending order : — 



I. Newcastle-under-Lyme Group. 

 II. Etruria Marl Group. 

 III. Black Band Group. 



* Trans. Hoy. Soc. Edin., vol. xxxrvi, p. 63, 1891. See especially pp. 65 and 68. 

 t l'foc. Roy. Phys. Soc. Edin., vol. xii, p. 228, 1894. 

 t See Quart. Journ. Geol. Soc, vol. lxi, 1905, p. 320. 



§ Memoirs of the Geological Survey of England and Wales: The Geology of the North Staffordshire Coalfields, 

 1905, p. 51. 



