this species existed in Europe as well as in America. I also saw in Mr. Peach's collection in 1870 some fragments which seemed to me distinct from Salter's species, and possibly belonging to _L. Gaspianum_.[BS] [BQ] "Report on Devonian Plants of Canada," 1871. [BR] "Observations sur quelques Plantes Fossiles des dépôts Devoniens." [BS] "Proceedings of the Geological Society of London," March, 1871. In the earliest description of _Psilophyton_ I recognised its probable generic affinity with Miller's "dichotomous plants," with Salter's "rootlets," and with Goeppert's _Haliserites Dechenianus_, and stated that I had "little doubt that materials exist in the Old Red Sandstone of Scotland for the reconstruction of at least one species of this genus." Since, however, Miller's plants had been referred to coniferous roots, and to fucoids, and Goeppert's _Haliserites_ was a name applicable only to fucoids, and since the structure and fruit of my plants placed them near to Lycopods, I was under the necessity of giving them a special generic name, nor could I with certainty affirm their specific identity with any European species. The comparison of the Scottish specimens with woody rootlets, though incorrect, is in one respect creditable to the acumen of Salter, as in almost any state of preservation an experienced eye can readily perceive that branchlets of _Psilophyton_ must have been woody rather than herbaceous, and their appearance is quite different from that of any true Algæ. The type of _Psilophyton_ is my _P. princeps_, of which the whole of the parts and structures are well known, the entire plant being furnished in abundance and in situ in the rich plant-beds of Gaspé. A second species, _P. robustius_, has also afforded well-characterised fructification. _P. elegans_, whose fruit appears as "oval scales," no doubt bore sac-like spore-cases resembling those of the other species, but in a different position, and perfectly flattened in the specimens procured. The only other Canadian species, _P. glabrum_, being somewhat different in appearance from the others, and not having afforded any fructification, must be regarded as uncertain. The generic characters of the first three species may be stated as follows: Stems dichotomous, with rudimentary subulate leaves, sometimes obsolete in terminal branchlets and fertile branches; and in decorticated specimens represented only by punctiform scars. Young branches circinate. Rhizomata cylindrical, with circular root-areoles. Internal structure of stem, an axis of scalariform vessels enclosed in a sheath of imperfect woody tissue and covered with a cellular bark more dense externally. Fruit, naked sac-like spore-cases, in pairs or clusters, terminal or lateral.