(_Lycopodites Vanuxemii_ of "Report on Devonian and Upper Silurian Plants," Part I., page 35, _L. plumula_ of "Report on Lower Carboniferous Plants," page 24, Plate I., Figs. 7, 8, 9.) In the reports above referred to, these remarkable pinnate, frond-like objects were referred to the genus _Lycopodites_, as had been done by Goeppert in his description of the European species _Lycopodites pennæformis_, which is very near to the American Erian form. Since 1871, however, there have been many new specimens obtained, and very various opinions expressed as to their affinities. While Hall has named some of them _Plumalina_, and has regarded them as animal structures, allied to hydroids, Lesquereux has described some of the Carboniferous forms under the generic name _Trochophyllum_, which is, however, more appropriate to plants with verticillate leaves which are included in this genus. Before I had seen the publications of Hall and Lesquereux on the subject, I had in a paper on "Scottish Devonian Plants"[BE] separated this group from the genus _Lycopodites_, and formed for it the genus _Ptilophyton_, in allusion to the feather-like aspect of the species. My reasons for this, and my present information as to the nature of these plants, may be stated as follows: Schimper, in his "Palæontologie Vegetale" (possibly from inattention to the descriptions or want of access to specimens), doubts the lycopodiaceous character of species of _Lycopodites_ described in my published papers on plants of the Devonian of America and in my Report of 1871. Of these, _L. Richardsoni_ and _L. Matthewi_ are undoubtedly very near to the modern genus _Lycopodium_. _L. Vanuxemii_ is, I admit, more problematical; but Schimper could scarcely have supposed it to be a fern or a fucoid allied to _Caulerpa_ had he observed that both in my species and the allied _L. pennæformis_ of Goeppert, which he does not appear to notice, the pinnules are articulated upon the stem, and leave scars where they have fallen off. When in Belfast in 1870, my attention was again directed to the affinities of these plants by finding in Prof. Thomson's collection a specimen from Caithness, which shows a plant apparently of this kind, with the same long narrow pinna? or leaflets, attached, however, to thicker stems, and rolled up in a circinate manner. It seems to be a plant in vernation, and the parts are too much crowded and pressed together to admit of being accurately figured or described; but I think I can scarcely be deceived as to its true nature. The circinate arrangement in this case would favour a relationship to ferns; but some lycopodiaceous plants also roll themselves in this way, and so do the branches of the plants of the genus _Psilophyton_. (Fig. 17, _supra_.) [BE] "Canadian Naturalist," 1878.