FOSSIL FERNS. SPHENOPTERIS.

Sphenopteris (wedge-leaf). [Lign. 18.]—The leaves are twice or thrice pinnated, the leaflets wedge-shaped, contracted or narrowest at their base, and more or less deeply lobed: the lobes divergent and palmated: the veins radiating from the base.

The ferns of this genus are extremely elegant, and comprise upwards of forty species. A beautiful Sphenopteris (S. affinis, Wond. p. 716,) occurs abundantly in the fresh-water carboniferous strata at Burdie House, near Edinburgh;[82] another elegant form, in coal-shale, is represented in [Lign. 18].

[82] See Dr. Hibbert's Memoir on the Strata and Fossils of Burdie House. 4to. 1835.

It is so rarely that the fructification of any species of Sphenopteris is preserved in a fossil state that I am induced to figure a leaflet of a remarkable plant, of this genus from the fluvio-marine oolitic deposits of Scarborough. [Lign. 19] is copied from the lithograph accompanying a notice of some rare plants from that locality, by the eminent botanist, C. J. F. Bunbury, Esq.[83]

[83] Geol. Journal, vol. vii. p. 179, pl. xii.

This fossil fern closely resembles certain species of Dicksonia (natives of New Granada). Each segment of the leaflet or pinnate is dilated at the apex into a reniform indusium; no capsules are visible, the fructification being, probably, in a young state.

Lign. 19. Sphenopteris nephrocarpa.
Inferior Oolite, Scarborough.
A magnified vein of a leaflet, showing the fructification at the extremities of the lobes, × two diameters.		Lign. 20. Sphenopteris Mantelli; nat.
Wealden, Tilgate Forest.

In the Wealden deposits, both of England and Germany, several species of Sphenopteris abound; one of which (Foss. Tilg. For. 1827), often occurs in the calciferous grit of Tilgate Forest, in a beautiful state of preservation: a small branch is figured in [Lign. 20]. This species is characterized by its slender and minutely divided wedge-shaped leaflets. The Sphenopteris Mantelli did not attain a considerable size; the largest stem I have seen indicated a plant of five or six feet in height. This Sphenopteris is sometimes associated with the remains of a beautiful plant of the genus Alethoptris,[84] the leaflets of which, in some examples, bear the fructification. (Wond. p. 394, Lign. 89.)

[84] Alethoptris elegans of Dr. Dunker. Mon. Norddeutschen Weald, pl. vii. fig. 7.