DISTRIBUTION. 153 



§ IV. DISTRIBUTION. 



It has been considered advisable, in order to give a graphic idea of the hori- 

 zontal distribution of the various species of the genera Carbonicola, Anthracomya, 

 and Naiadites, that diagrammatic sections of each of the coal-fields and of other 

 Carboniferous strata in which they occur should be given. I have therefore 

 compiled such a series of stratigraphical tables from actual pit-sections, and also 

 from vertical tables given of the various Coal-fields in the ' Memoirs of the 

 Geological Survey,' and in Professor Hull's ' Coal-fields of Great Britain.' 

 These sections are only intended to show the succession of strata and relative 

 position of the shell-bearing beds in the various districts, and, except where 

 indicated, are not drawn to scale. Wherever the species occurring in any bed are 

 given, I have personally identified them in Collections; and the localities in these 

 lists are therefore more definite and more accurate than those in the text. Of 

 course there are probably many more horizons at which mussel-bands occur, but 

 these have either not been recorded, or no specimen from them has come to hand 

 for identification. 



I am specially indebted to Mr. James W. Kirkby and Mr. John Smith for the 

 sections of the Fifeshire and Ayrshire Coal-fields, and to the former also for 

 permission to copy his section of the Calciferous Sandstone Series of Fife. In 

 those cases where no section of a coal-field mentioned in the text is given, the 

 omission is due to the absence of the necessary detailed information. 



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