Both in Canada and the United States that part of the great Erian system which may be regarded as its middle division, the Hamilton and Marcellus shales of New York, the Cordaites shales of St. John, New Brunswick, and the middle shales and sandstones of the Gaspé series, presents conditions more favourable to the abundant growth of land-plants than either the upper or lower member. In the St. John beds, in particular, there is a rich fern flora, comparable with that of the coal-formation, and numerous stipes of ferns and trunks of tree-ferns have been found in the Hamilton and Corniferous series in the West, as well as trunks of _Dadoxylon_. It is, however, distinguished by a prevalence of small and delicate species, and by such forms as _Hymenophyllites_ and the smaller Sphenopterids, and also by some peculiar ferns, as _Archæopteris_ and _Megalopteris_. In addition to ferns, it has small _Lepidodendra_, of which _L. Gaspianum_ is the chief. _Calamiteæ_ occur, _Archæocalamites radiatus_ being the dominant species. This plant, which in Europe appears to reach up into the Lower Carboniferous, is so far strictly Erian in northeast America. _Sigillariæ_ scarcely appear, but _Cordaites_ is abundant, and the earliest known species of _Dadoxylon_ appear, while the Psilophyton, so characteristic of the Lower Erian, still continues, and the remarkable aquatic plants of the genus _Ptilophyton_ are locally abundant. (3) _Lower Erian Sub-Flora_: This belongs to the Lower Devonian sandstones and shales, and is best seen in that formation at Gaspé and the Bay des Chaleurs. It is equivalent to the Oriskany sandstone, so far as its animal fossils and mineral character are concerned. It is characterised by the absence of true ferns, _Calamites_ and _Sigillariæ_, and by the presence of such forms as _Psilophyton_, _Arthrostigma_, _Leptophleum_, and _Nematophyton_. _Lepidodendron Gaspianum_ and _Leptophleum_ already occur, though not nearly so abundant as Psilophyton. The Lower Erian plants have an antique and generalised aspect which would lead us to infer that they are near the beginning of the land-flora, or perhaps in part belong to the close of an earlier flora still in great part unknown and few indications of land-plants have been found earlier. At Campbellton and Scaumenac Bay, on the Bay des Chaleurs, fossil fishes of genera characteristic of the Lower and Upper Devonian horizons respectively, occur in association with fossil plants of these horizons, and have been described by Mr. Whiteaves.[FP] [FP] "Transactions of the Royal Society of Canada." It is interesting to note that, as Fontaine and White have observed, certain forms which are Erian in the northeast are found in the Lower members of the Carboniferous in West Virginia, indicating the southward march of species in these periods. 3. The Silurian Flora and still Earlier Indications of Plants.