CARBONIFEROUS BRACHIOPODA. 
251 
tains remains of plants, and more rarely Orthoceras and other marine shells."^ Tlie Coal- 
measures, as stated in the section, are from 10,000 to 12,000 feet thick, and consist of 
alternations of sandstone, shale, fire-clay or mider-clay, coal, and ironstone. 
At page 133 of the same Manual Prof. Ramsay remarks, " It is impossible to have 
an intimate knowledge of the Carboniferous rocks, even within the limited area of the 
British Islands, without coming to the conclusion that the various strata were formed in 
seas, some comparatively open and deep, some shallow, estuarine, and restricted in area, and 
some in fresh water ; and, second, that the beds of Coal were due to terrestrial vegetable 
growths that flourished and died on the land, and were buried with the soils on which 
they grew. To examine all these points in full detail would require the writing of a 
special treatise." See Godwin-Austen, ' Quart. Journ. Geol. Soc.,' vol. xii, p. 42, &c. 
The explanations of the Sheets of the Geological Maps of England, Wales, and 
Ireland contain also many details and lists of Brachiopoda, for which there is not 
space in these pages. In the sequel, allusion will be made to Scotland separately, as 
the species of Brachiopoda in that portion of the United Kingdom have been most 
carefully referred to their precise horizons. 
A very important and able memoir by Prof. Edward Hull, M.A., F.R.S., " On the 
Upper Limit of the Essentially Marine Beds of the Carboniferous Groups of the British 
Isles and adjoining Continental Districts, with suggestions for a fresh classification of the 
Carboniferous series," has been published in p. 613 et seq. of the thirty-third volume of 
the ' Quarterly Journal of the Geological Society,' 1877. 
At p. 615 of his memoir Prof. Hull gives the following succession (see next page) 
of the strata in the British Carboniferous districts as now generally recognised,^ and for 
the purpose of easy reference has arranged them into stages. 
^ The reader's attention is invited to a paper by D. C. Davies, E.G.S., "On the Millstone-Grit 
of the North-Wales Border," published in the ' Geological Magazine,' vol. vii, February and March, 1870 ; 
also to memoir by W. Prosser, F.G.S,, "On the Fossiliferous character of the Millstone-Grit of Sweeney, 
near Oswestry, Shropshire," 'Geol. Mag.,' vol. ii, p. 107, 1805. Spirifer bisulcatus, an J(hi/ris, Prod, 
semireticulatus, JP. costatus, Strejitorhynchm crenistria, are alluded to. 
2 'Coal-Fields of Great Britain,' 3rd edit., p. 80. Index-sheet of Formations of the Geological 
Survey Map, 1871. 
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