In the description of examples of _Lycopodites_ and _Selaginellites_ I have confined myself to such as appear to be above suspicion either because of the presence of spore-bearing organs or, in a few cases, because the specimens of sterile shoots are sufficiently large to show the form of branching in addition to the texture of the leaves. The two generic names _Lycopodites_ and _Selaginellites_ are employed for fossil species which there are substantial grounds for regarding as representatives of _Lycopodium_ and _Selaginella_. The designation _Selaginellites_ is adopted only for species which afford evidence of heterospory; the name _Lycopodites_, on the other hand, is used in a comprehensive sense to include all forms—whether homophyllous or heterophyllous—which are not known to be heterosporous. This restricted use of the generic name _Selaginellites_ is advocated by Zeiller[173], who instituted the genus, and by Halle[174] in his recent paper on herbaceous lycopods. Lycopodites. The generic term _Lycopodites_ was used by Brongniart in 1822[175] in describing some Tertiary examples of slender axes clothed with small scale-like leaves which he named _Lycopodites squamatus_. These are fragments of coniferous shoots. In the _Prodrome d’une histoire des végétaux fossiles_[176] Brongniart included several Palaeozoic and Jurassic species in _Lycopodites_ and instituted a new genus _Selaginites_, expressing a doubt as to the wisdom of attempting to draw a generic distinction between the two sets of species. In a later work[177] he recognised only one undoubted species, _Lycopodites falcatus_. The first satisfactory account of fossils referred to _Lycopodites_ is by Goldenberg[178] who gave the following definition of the genus:—“Branches with leaves spirally disposed or in whorls. Sporangia in the axil of foliage leaves or borne in terminal strobili.” It was suggested by Lesquereux[179] that Goldenberg’s definition, which was intended to apply to herbaceous species, should be extended so as to include forms with woody stems but which do not in all respects agree with _Lepidodendron_. Kidston[180] subsequently adopted Lesquereux’s modification of Goldenberg’s definition. We cannot draw any well-defined line between impressions of herbaceous forms and those of small arborescent species. We use the name _Lycopodites_ for such plants as appear to agree in habit with recent species of _Lycopodium_ and _Selaginella_ and which, so far as we know, were not heterosporous: it is highly probable that some of the species so named had the power of producing secondary wood, a power possessed by some recent Pteridophytes which never attain the dimensions of arborescent plants.