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_. [Illustration: Lign. 21. Cyclopteris trichomanoides; _a single leaflet_; _nat._ _Oolite, near Scarborough._] Cyclopteris (_round-leaf_). _Lign. 21._--The frond is simple and entire, or but slightly lobed at the margin, and generally orbicular, or kidney-shaped: there is no midrib; the veins are numerous, equal, and dichotomous, or forked, and radiate from the base. The form and disposition of the veins resemble those of some living species of fern; the absence of a median rib, or vein, is the most striking character of this genus. The fructification is supposed to have been marginal. [Sidenote: FOSSIL FERNS. NEUROPTERIS.] Neuropteris (_nerved-leaf_). _Lign. 22._--The fronds are pinnate or bipinnate; the leaflets more or less ovate or cordiform and entire, adhering to the rachis by their centre only; veins very fine, arched, rising obliquely from the base of the leaflet; the midrib does not extend' to the apex of the leaflets, but terminates by subdividing into veins. [Illustration: Lign. 22. Neuropteris acuminata; _nat._ _In Coal-shale, Yorkshire._] This is a very numerous genus, comprising thirty or more species, which are principally found in the coal-shale. Some of these plants bear a general resemblance to the _Osmunda regalis_, but differ in their essential characters; their leaflets often form the nuclei of ironstone nodules. Glossopteris (_tongue-leaf_). _Lign. 23._--Leaves simple, sub-lanceolate, gradually contracting towards the base; midrib thick at the base, and vanishing towards the apex of the leaf; veins very fine, curved, oblique, frequently dichotomous, sometimes reticulated, or anastomosing at their base. The plants of this genus resemble the ferns with simple leaves. A few species only are known; of these, two are from the coal-shale, one from the Lias, and one from the oolite. [Illustration: Lign. 23. Glossopteris Phillipsii; _nat._ _Oolite, Scarborough._] [Illustration: Lign. 24. Odontopteris Schlotheimii; _nat._ _Coal-shale of Saxony._]