Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/720

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Thus, taking the lacustrine formation of the Upper Old Red Sandstone as the basis for the succeeding Carboniferous system, we ascend through a vast series of essentially marine strata with oceanic beds, until we reach the top of the Gannister stage, where a change occurs in the character of the fossil forms, and the marine molluscs give place to those of freshwater or estuarine characters. I hope to be able to show that this change is coextensive with the British Isles and at least the neighbouring European Carboniferous districts.

We now come to the consideration of the Carboniferous series of Ireland, taking the districts in the order indicated above.