2. The Lower Coal-formation Conglomerate and Chester groups of Illinois (Worthen).
3. The Lower Carboniferous Sandstone of Kentucky, Alabama, and Virginia.
4. The Millstone Grit and Yoredale rocks of northern England, and the Culmiferous of Devonshire.
5. The Moor rock and Lower Coal-measures of Scotland.
6. Flagstones and Lower Shales of the south of Ireland, and Millstone Grit of the north of Ireland.
7. The Jüngste Grauwacke of the Hartz, Saxony, and Silesia.
(4) The Carboniferous Limestone Series:
This affords few fossil plants in eastern America, and in so far as known they are similar to those of the next group. In Scotland it is richer in plants, but, according to Mr. Kidston, these are largely similar to those of the underlying beds, though with some species which extend upward into the Millstone Grit. In Scotland the alga named Spirophyton and Archæocalamites radiatus—which in America are Erian—appear in this formation.
(5) The Lower Carboniferous Sub-Flora:
This group of plants is best seen in the shales of the Horton series, under the Lower Carboniferous marine limestones. It is small and peculiar. The most characteristic species are the following: