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Updated: May 6, 2025
Lingula, most persistent throughout all geological time, is abundant in the coal-shales, but not in the limestones. Aviculopecten is there abundant also. Fenestella retipora. Goniatites. We have evidence of the existence in the forests of a variety of centipede, specimens having been found in the erect stump of a hollow tree, although the fossil is an extremely rare one.
This uniformity of structure in the shales over wide areas is a well ascertained characteristic of the coal-shales, and we may therefore regard the method of their deposition as given here with a degree of certainty. There is a class of deposit found among the coal-beds, which is known as the "underclay," and this is the most regular of all as to the position in which it is found.
In the last mentioned case, only the impression remained, but the carbonaceous matter had gone to stain the surrounding clay black, thus indicating that the dark colour of the coal-shales is due to the carbon derived from the plants which they included. Another very prominent member of the vegetation of the coal period, was that order of plants known as the Calamites.
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