Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/514

 fossil. No botanist dealing with living plants would venture on such materials to decide on their place, far less to describe them as forming a new species. It is very different with fossils belonging to the animal kingdom, where the portion of the organism preserved is generally that which is employed to a greater or less extent in the classification of recent forms. I must therefore adhere to the system of nomenclature I have hitherto followed, notwithstanding that it has been censured by so distinguished a botanist as Prof. Heer (Flora Foss. Arct. p. 84), and consider this a species of Osmundites. It is no answer to this method to say that species of plants now living found in quaternary deposits, being so far fossil, ought to receive another name ; for if the materials are sufficient to determine with certainty the specific identity of the two plants, of course, on the principle I adopt, the same name must be applied to both. It still seems to me of great importance to be able to distinguish the extinct from the existing species by the name, inasmuch as this distinction conveys also to the student, to some extent, the value of the evidence on which the species has been established.

The fossil has been a larger plant than our recent Osmunda regalis, or than a similar stem found in a mass of " Susswasserquarz " near Schemnitz, figured by Pettko under the name Asterochloena schemniciensis in Haidinger's Abhandl. vol. iii. (1850) p. 163, pl. xx.,. but afterwards referred by linger to Osmundites (Denkschr. d. K. K. Akad. d. Wiss. vol. vi. (1 853). I propose to associate with it the name of George Dowker, Esq., F.G.S., from whom I received the specimen, and to name it Osmundites Dowkeri. It was found on the shore at Herne Bay, and could have been obtained only from the Lower Eocene beds there — perhaps from the beds below the London Clay.

A group of fern stems are found in the later Palaeozoic and in the earlier Mesozoic strata which are nearly allied to those of Osmunda. They have been, unnecessarily, divided into several genera ; but as they all agree in having a slender caudex covered by the long ascending and permanent bases of the petioles, and numerous aerial roots, it seems better to unite them under Corda's genus Chelepteris. The materials are not sufficient to determine with any thing like precision the position of this group of stems ; but in the characters I have just given they agree with the recent Osmundaceoe, as well as in having the vascular bundle of their petioles simple. There is at least a fair presumption that this is their position ; yet it must be remembered that these characters are not peculiar to this recent tribe, but that they are found also in ferns widely separated from them in a natural classification, as, for instance, in Dicksonia antarctica. The genus Chelepteris, extended as I propose, would include the following species : —

From the Permian of Russia (Gres cuivreux of Orenbourg) : —

Thamnopteris Schlechtendalii, Brongn. Tabl. Genr. Foss. p. 36.

Bathypteris rhomboidea, Eichw. Leth. Ross. vol. i. p. 96.

Anomorrhoea Fischeri, Eichw. Leth. Ross. vol. i. p. 102.

Chelepteris gracilis, Eichw. Leth. Ross. vol. i. p. 98.