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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