This species was fully described by me in the papers referred to above, from specimens obtained from the rich exposures at Gaspé Bay, and which enabled me to illustrate its parts more fully, perhaps, than those of any other species of so great antiquity. In the specimens I had obtained I was able to recognise the forms of the rhizomata, stems, branches, and rudimentary leaves, and also the internal structure of the stems and rhizomata, and to illustrate the remarkable resemblance of the forms and structures to those of the modern _Psilotum_. The fructification was, however, altogether peculiar, consisting of narrowly ovate sporangia, borne usually in pairs, on curved and apparently rigid petioles. Under the microscope these sporangia show indications of cellular structure, and appear to have been membranous in character. In some specimens dehiscence appears to have taken place by a slit in one side, and, clay having entered into the interior, both walls of the spore-case can be seen. In other instances, being flattened, they might be mistaken for scales. No spores could be observed in any of the specimens, though in some the surface was marked by slight, rounded prominences, possibly the impressions of the spores within. This peculiar and very simple style of spore-case is also characteristic of other species, and gives to _Psilophyton_ a very distinct generic character. These naked spore-cases may be compared to those of such lycopodiaceous plants as _Psilotum_, in which the scales are rudimentary. They also bear some resemblance, though on a much larger scale, to the spore-cases of some Erian ferns (_Archæopteris_), to be mentioned in the sequel. On the whole, however, they seem most nearly related to the sporocarps of the Rhizocarpeæ. [Illustration: Fig. 21.--_Lepidodendron_ and _Psilophyton_ (Erian, New Brunswick). A, _Lepidodendron Gaspianum_. B, C, _Psilophyton elegans_.] _Arthrostigma_, which is found in the same beds with Psilophyton, was a plant of more robust growth, with better-developed, narrow, and pointed leaves, borne in a verticillate or spiral manner, and bearing at the ends of its branches spikes of naked sporocarps, apparently similar to those of _Psilophyton_ but more rounded in form. The two genera must have been nearly related, and the slender branchlets of _Arthrostigma_ are, unless well preserved, scarcely distinguishable from the stems of _Psilophyton_.[AU] [AU] Reports of the author on "Devonian Plants," "Geological Survey of Canada," which see for details as to Erian Flora of northeastern America.