248 Hind: Carboniferous Geology. 



faunas have been found above the Dibunophyllum zone of the 

 Limestone, the Grits succeed immediately the Yoredale Series 

 with a Productus giganteus fauna, and this is the case in North- 

 umberland also, but in Scotland, as I have mentioned above, 

 a peculiar fauna with Prothyris elegans, hitherto known only 

 from the Coal Measures of Nebraska, U.S.A., is typical of 

 the beds which intervene between the Upper Dibunophyllum 

 beds and the Coal Measures. The Grits are the detritus of a 

 granite country, which local distribution seems to indicate as 

 having occupied a position to the North-East. 



Many fossil horizons are known in the shales, which separate 

 the different beds of Grit from each other. I published all the 

 information I then had on the subject in ' The Naturalist,' 

 1907, pp. 17-23 and 90-99, and unfortunately I have nothing 

 fresh to add. The Grits themselves contain plant remains, 

 and they, however, furnish the following very important piece 

 of evidence. The flora of the Millstone Grit is allied to the 

 Upper or Coal Measure flora in distinction to the flora of the 

 Pendleside Series and Carboniferous Limestone Series, which 

 is characterised by a lower Carboniferous flora. The flora is 

 therefore the index to the Series, and no beds should be assigned 

 to the Millstone Grit, which are characterised by the lower 

 flora, nor can we be always certain in the absence of the flora, 

 whether any Grit is the representative of Millstone Grit or 

 earlier beds ; for example, the so-called Millstone Grit of 

 Bristol probably represents in time a part of the Pendleside 

 Series. 



The Millstone Grit Series of England appears to have no 

 fauna of its own. In the neighbourhood of Halifax we find 

 the persistence of a late Pendleside fauna as high as the third 

 Grit, and in the neighbourhood of Harrogate is a Calcareous 

 Grit, the Cayton Gill beds, in which a late Dibunophyllum 

 fauna seems to have reappeared. 



In the Carboniferous succession of Denbighshire, the Mill- 

 stone Grit is probably only represented by 100 feet of beds, 

 including the Aqueduct Grit. 



It is difficult to conceive the exact conditions under which 

 a deposit, averaging from 500-100 feet over an extensive area, 

 suddenly becomes enormously thick o\'er a limited district 

 to between 2000 and 3000 feet. Whatever it was, the cause 

 is intimately connected with the origin of the Pendleside Series, 

 itself a very local deposit, for the greatest thickness of the Mill- 



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