10 CARBONIFEROUS LAMELLIBRANCHIATA. 



Carboniferous beds. Messrs. Hall, Usher, and H. B. Woodward still retain the 

 term Upper Devonian for the Marwood and Pilton beds. The mere occurrence of 

 a few forms common to other formations does not amount to undoubted evidence 

 for the classification of the two beds under the same system. All that can be 

 affirmed is that there was a gradual sequence between the two formations, 

 deposition going on without any break or unconformity, and that the changes in 

 environment were such that certain forms of life were unaffected by the alteration 

 of conditions. The direct connection of the Devonian and Carboniferous epochs 

 by passage beds is not only evident in Devonshire ; passage beds are also found 

 in the Forest of Dean, in Shropshire, as the Farlow beds, in the Lake District, 

 and in the Isle of Man, but in these cases the palseontological evidence is small 

 and unimportant. 



From the palceontological point of view of this Monograph the upper limit of 

 the Carboniferous rocks is not important. The upper red beds of the Coal 

 Measures contain a fauna from which molluscan remains are almost entirely absent, 

 with the exception of Anthracomya PhiUipsvi and a few microscopic shells, which 

 have been found in the upper measures at Slade Lane, Manchester, by Mr. Roeder. 

 Doubtless much of the ground in Staffordshire and Warwickshire now mapped as 

 Permian should really, on lithological grounds and from the fossil flora contained 

 in the beds, be more correctly grouped as Upper Carboniferous. 



It will have become apparent from the foregoing pages that it is impossible 

 to convey adequate information as to the British Carboniferous rocks in one 

 single classification. 



In English text books the succession of Carboniferous rocks in the North 

 Midlands and Yorkshire is generally given as typical of the period. A comparison, 

 however, with the general succession in Scotland, Ireland, and Devonshire will at 

 once show the local character of this classification. The following schemes, with 

 the general sequence in different localities arranged side by side, will give some 

 idea of the very local character of much of the Carboniferous deposits ; and it 

 appears to the writer that a twofold classification of Carboniferous rocks would be 

 more accurate than the threefold one that is at present generally in use. But 

 even then there is no accurate line of demarcation between the lower shales and 

 grits of the Millstone Grit series and the upper beds of the Carboniferous 

 Limestone and Yoredale strata. Mr. R. Kidston^ is, I see, also of this opinion, 

 and his views are based on the distribution of the Carboniferous flora. This 

 classification is as follows : 



Uppek Cabbonifeeous or^ rCoal Measures. 

 Antheacifeeocs seeies j iMillstone Grit series. 



1 ' Proc. Eoy. Phys. Soc. Edin.,' vol. xii, 1893-4, p. 222. 



