Psilotum, with which these plants very closely correspond in all except their rhizomes and the circinate terminations of the branchlets. The name proposed above is intended to express this relation, as well as the most apparent distinction between these plants and those of the genera Lycopodites and Selaginitest. To the species above described I would give the name of Psilophyton princeps. I have attempted a restoration of its general appearance in fig. 1 f.

Fig. 2 g, longitudinal section of stem, nat. size; h, cortical cells (300 diams.); i, parenchyma (300 diams.); k, scalariform tissue of axis (300 diams.)

Some of my specimens appear to indicate a second species, characterized by more robust stems, more finely ridged, and having slender alternate branches, which bifurcate frequently and usually bend downward. The specimens are not well preserved, but are very distinct from P. princeps, while probably generically related to it. I would name this species P. robustius.

* See Brongniart, Vég. Fos. vol. ii. pls. 6 & 11. I have been favoured by Prof. Gray, of Harvard College, with specimens of P. flavidum from Tahiti and P. triquetrum from Australia, which closely resemble the fossils in structure and surface-markings.

† I should have preferred the term "Psilotites;" but this has been preoccupied by a Jurassic plant, of which, however, I cannot find any detailed description. See Unger, Gen. et Spec, &c. p. 279; Brongniart, Tableau des Genres, p. 41.

Neither of the species exhibit distinct fructification. Certain obscurely cuneate carbonaceous spots attached to the sides of the branches of P. princeps are, perhaps, of this character; and the object represented in fig. 1 e, which appears to be thus attached, may be an example in better preservation than usual. It consists of four thick lanceolate leaves or bracts with single midrib, arising from a flattened carbonaceous patch, which shows traces of similar leaves on its surface. These leaves or bracts have evidently enclosed the fructification of some lycopodiaceous plant; and from their association with Psilophyton princeps, I regard it as highly probable, though by no means certain, that they belong to that species.

The rhizomata of Psilophyton princeps occur in situ in a number of argillaceous beds, in a manner which shows that they crept in immense numbers over flats of sandy clay, on which their graceful stems must have formed a thick, but delicate, herbage, rising to the height of from two to four feet. The rhizomes and the bases of the stems may possibly have been submerged; but I should infer, from the appearance and structure of the latter, that they were rigid, woody, and perhaps brittle. In many beds in which the rhizomes have not been distinctly preserved, the vertical rootlets remain, producing an appearance very similar to that of the Stigmarian under-clays of the coal-measures. Sir W. E. Logan has noted in his detailed sections numerous cases of this kind.

When broken into fragments and imperfectly preserved, Psilophyton princeps presents a variety of deceptive appearances. When perfectly compressed in such a manner as to obliterate the markings, it might be regarded as a dichotomous fucoid or a flattened root. When decorticated and exhibiting faint longitudinal striæ, it presents, especially when the more slender branchlets are broken off, the aspect of a frond of Schizopteris or Trichomanites. When rendered hollow by decay, it forms bifurcating tubules, which might be regarded as twigs of some tree with the pith removed. Lastly, the young plants might be mistaken for ferns in a state of vernation. In all conditions of preservation, the stems, rhizomes, and rootlets, if separated, might be referred to distinct genera. I have little doubt therefore that many imperfectly preserved Devonian plants of this general form, noticed under various names by authors, may belong to this genus, and some of them to the species above described. In particular I may refer

to certain dichotomous fucoids in the genera Fucoides and Chondrites; to a plant from the Hamilton Group of New York, figured by Vanuxem in his Report, p. 161; to the dichotomous roots from Orkney and Caithness described by Mr. Salter in the 'Proceedings' of this Society for last year; and to the bifurcating plants with curved tendril-like branchlets figured by Hugh Miller, 'Old Red Sandstone,' plate 7, and 'Testimony of the Rocks, p. 434. From the description in the former work, Chap. 5, it would appear that the author had observed not only the stems but the rhizomes with their Stigmaria-like areoles, though without suspecting them to belong to the same plant. I have little doubt therefore that materials exist in the Old Red Sandstone of Scotland for the reconstruction of at least one species of this genus. Various fragments which I have collected induce me to believe that it may be found also in the Lower Coal-measures.

I have noticed above the resemblance of flattened specimens of Psilophyton to ferns of the genus Trichomanites (Goeppert.) To this genus, indeed, I was disposed to refer the specimens, until I found that the internal structure was lycopodiaceous, and that the branching filaments are true branchlets covered with minute leaves. A comparison of the plants above described with Trichomanites Beinertii of Goeppert, and Sphenophyllum (T.) bifidum of Lindley and Hutton, will show at a glance the strong resemblance that subsists; and, since the specimens on which these species are founded do not appear to have exhibited internal structure or venation, I think it still admits of a doubt whether they are really ferns. By way of further caution on this point, I may remark that in flattened stems, either of Psilotum or of its ancient relative, the slender woody axis may leave a mark resembling the nervure of a leaf, and thus complete the resemblance to a frond of Trichomanes.

Since writing the above, Professor G. S. Newberry has kindly pointed out to me the close resemblance between the first species above described and Haliserites Dechenianus of Goeppert ('Flora der Uebergangsgebirges,' p. 88). I can scarcely doubt that this so-called fucoid is in reality a plant of the genus above described, but in such a state of compression that the stem appears like a narrow frond, and the woody axis as a midrib. As this plant is said to occur very abundantly at certain levels in the Devonian Series of the Rhine, if my suspicions as to its nature are correct

further examination might disclose its rhizomes, leaves, or fructification.*

2. LEPIDODENDRON. (Fig. 3.)

A single species of this genus is found rather plentifully in the beds containing the plants just described, and is distinct from any that I have observed in the Coal-formation. The specimens observed were all of small size and fragmentary, nor was their state of preservation very good, though most of them were

Fig. 3. Lepidodendron Gaspianum. a, decorticated stem and leaves; b, areoles; c, small branch and leaves.

accompanied by the leaves. In specimens about two inches in diameter, the areoles are two lines in length and one in breadth, and placed closely together. They are elliptical, acuminate, with central leaf-scar, the form and markings of which could not be perceived. The leaves are thick at the base and short, slightly ascending, and then curving downward. The branches are slender, straight, and very uniform in thickness in the portions observed. This plant may be identical with the L. Chemungense of Hall, from the Devonian rocks of New York; but I am not aware that any specimens of that species hitherto observed show the leaf-scars or leaves; and, when these are obtained, should the present species prove distinct, I would name it L. Gaspianum. Its characters, as above stated, are represented in figs. 3 a-c.

It is possible that some of the fragments, from the Devonian of the Thüringerwald, included by Prof. Unger in his order Rhachiopteridea may be allied to Psilophyton. (See Denkschr. Kais. Akad. Wissen. Wien, vol. xi. p. 139.)

† L. (Sagenaria) Veltheimianum, another ancient and widely distributed species, resembles the above in the form of the areoles and position of the scars; but the leaves and young branches differ, and my specimens show no median furrow in the areoles. L. nothum (Unger) also seems closely allied.

3. PROTOTAXITES, gen. nov. (Fig. 4.)

Woody trunks with concentric rings of growth and medullary rays. Cells of pleurenchyma scarcely in regular series, thickwalled, and cylindrical, with a double series of spiral fibres. Disc-structure indistinct in the specimens observed.

I propose the above generic appellation for a tree having the spirally marked cells characteristic of the genera Taxites and Spiropitys of Goeppert, but differing from any conifer known to me in the cylindrical form and loose aggregation of the woodcells, as seen in the cross-section, in which particular it more

Fig. 4. Prototaxites Logani. a, cross-section, magnified 40 diams., showing growth-line and medullary ray; b, longitudinal section (300 diams.); c, transverse section (300 diams.)

nearly resembles the young succulent twigs of some modern conifers than their mature wood. A fine silicified trunk of this tree was brought from Gaspé by Sir W. E. Logan, and was shortly described in the 'Proceedings of the American Association' for 1856.