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: _Dadoxylon_ (_Palæoxylon_) _antiquius_, Dn.--A species with large medullary rays of three or more series of cells. _Lepidodendron corrugatum_, Dn.--A species closely allied to _L. Veltheimianum_ of Europe, and which is its American representative. This is perhaps the most characteristic plant of the formation. It is very abundant, and presents very protean appearances, in its old stems, branches, twigs, and _Knorria_ forms. It had well-characterised stigmaria roots, and constitutes the oldest erect forest known in Nova Scotia. _Lepidodendron tetragonum_, Sternberg. _L. obovatum_, Sternb. _L. aculeatum_, Sternb. _L. dichotomum_, Sternb. The four species last mentioned are comparatively rare, and the specimens are usually too imperfect to render their identification certain, but Lepidodendra are especially characteristic trees of this horizon. _Cyclopteris_ (_Aneimites_) _Acadica_, Dn.--A very characteristic fern, allied in the form of its fronds to _C. tenuifolia_ of Goeppert, to _C. nana_ of Eichwald, and to _Adiantites antiquus_ of Stur. Its fructification, however, is nearer to that of _Aneimia_ than to that of _Adiantum_. Ferns of the genera Cardiopteris and _Hymenophyllites_ also occur, though rarely. _Ptilophyton plumula_, Dn.--This is the latest appearance of this Erian genus, which also occurs in the Lower Carboniferous of Europe and of the United States. _Cordaites borassifolia_, Brongt. On the whole, this small flora is markedly distinct from that of the Millstone Grit and true coal-formation, from which it is separated by the great length of time required for the deposition of the marine limestones and their associated beds, in which no land-plants have been found; nor is this gap filled up by the conglomerates and coarse arenaceous beds which, as I have explained in "Acadian Geology," in some localities take the place of the limestones, as they do also in the Appalachian region farther south. The palæobotanical and stratigraphical equivalents of this series abroad would seem to be the following: 1. The Vespertine group of Rogers in Pennsylvania. 2. The Kinderhook group of Worthen in Illinois. 3. The Marshall group of Winchell in Michigan. 4. The Waverley sandstone (in part) of Ohio. 5. The Lower or False Coal-measures of Virginia. 6. The Calciferous sandstones of McLaren, or Tweedian group of Tate in Scotland. 7. The Lower Carboniferous slate and Coomhala grits of Jukes in Ireland. 8. The Culm and Culm Grauwacke of Germany. 9. The Graywacke or Lower Coal-measures of the Vosges, as described by Schimper. 10. The Older Coal-formation of the Ural, as described by Eichwald.