The restoration, after Nathorst[947], shown in fig. 281 illustrates the habit of this striking fern, examples of which or of closely allied species are recorded from Rhaetic rocks of Germany, Scania, Persia, Bornholm, Tonkin, China, and elsewhere[948]. The petiole, reaching a length of 60 cm., forks at the apex into two equal arms leaving between them an oval space and occasionally crossing one another. The axes of these branches are twisted so that the pinnae, which may be as many as 24 on each arm, and arise from the inner side, by torsion of the axes assume an external position. An interesting analogy as regards the twisted rachis of _Dictyophyllum exile_ and _Camptopteris_ is afforded by the leaves of the Cycads, _Macrozamia Fawcettiae_ and _M. corallipes_, which are also characterised by the torsion of the rachis. The habit, justly compared by Nathorst with that of _Matonia pectinata_, affords another illustration of the common occurrence in older ferns of a dichotomous system of branching. The pinnae, characterised by circinate vernation, reach a length of 60 cm. and are divided into linear lobes inclined obliquely or at right angles to the pinna axis. The whole of the under surface of the lamina may be covered with sporangia, 4–7 sporangia in each sorus; the annulus is incomplete and approximately vertical (fig. 282, D). The rhizome is probably represented by the dichotomously branched axis described by Nathorst from Scania as _Rhizomopteris major_; the leaf-scars show a horse-shoe leaf-trace. [Illustration: FIG. 282. A. _Dictyophyllum Nilssoni._ B. _Rhizomopteris Schenki._ C. _Camptopteris spiralis._ D, E. _Dictyophyllum exile._ (After Nathorst; A, B, C, E, ⅔ nat. size.)] _Dictyophyllum Nathorsti_ Zeiller[949]. This type, represented by a splendid series of specimens from the Rhaetic beds of Tonkin, agrees very closely with _D. exile_. It differs, however, in the basal parts of the pinnae which are concrescent for a length of 5 to 8 cm. instead of free as in _D. exile_; and, to a slight degree, in the form of the ultimate segments. In habit and in soral characters the two species are practically identical. Each sorus contains 5 to 8 sporangia, which are rather larger than those of _Dipteris_. _Dictyophyllum rugosum_, Lind. and Hutt. Fig. 283. 1828. _Phlebopteris Phillipsii_, Brongniart, Hist. vég. foss. p. 377, Pl. CXXXII. fig. 3; Pl. CXXXIII. fig. 1. 1829. _Phyllites nervulosis_, Phillips, Geol. Yorks. p. 148, Pl. VIII. fig. 9. 1834. _Dictyophyllum rugosum_, Lindley and Hutton, Foss. Flor. II. Pl. CIV. 1836. _Polypodites heracleifolius_, Goeppert, Foss. Farn. p. 344. 1849. _Camptopteris Phillipsii_, Brongniart, Tableau, p. 105. 1880. _Clathropteris whitbyensis_, Nathorst, Berättelse, p. 83.