This species, which is characteristic of Jurassic rocks, is less completely known than the two types described above, but in the form and venation of the pinnae there is little difference between the Rhaetic and Jurassic plants. The leaves of the Jurassic species appear to have been smaller and more like those of _Dipteris conjugata_ (fig. 231); there are no indications of the existence of the two curved arms at the summit of the petiole which form so striking a feature in _D. exile_ and _D. Nathorsti_. No sporangia have been found on English specimens, but it is safe to assume their agreement with those of other species. A more complete list of records of _D. rugosum_ is given in the first volume of the British Museum Catalogue of Jurassic plants[950]. [Illustration: FIG. 283. _Dictyophyllum rugosum_ (Lind. and Hutt.). (Brit. Mus. Nat. size.)] Nathorst[951] has recently drawn attention to certain differences between _Dictyophyllum_ and _Dipteris_. The pinnate division of the pinnae is not represented in the fronds of the recent species, but this method of lobing, which is a marked characteristic of _Dictyophyllum_, is less prominent in _Clathropteris_; and in _Camptopteris lunzensis_ Stur[952], an Austrian Upper Triassic species, the pinnae are entire. In _Dictyophyllum_ the sori cover the whole lower surface of the leaf; in _Dipteris_ they are more widely separated and the sporangia have a diameter of 0·02 mm., but in _Dictyophyllum_ the diameter is 0·4–0·6 mm. Moreover in _Dictyophyllum_ the sori contain 5 to 8 sporangia, whereas in _Dipteris_ they are much more numerous. Despite these differences it is clear, as Nathorst says, that _Dictyophyllum_, _Clathropteris_, and _Camptopteris_ are existing types very closely allied to _Dipteris_. It is a matter of secondary importance whether we include all in the Dipteridinae or follow Nathorst’s suggestion and refer the fossil genera to the separate family Camptopteridinae. _Thaumatopteris._ This genus, founded by Goeppert[953] for a Rhaetic plant from Bayreuth, is by some authors[954] regarded as identical with _Dictyophyllum_, but it has recently been resuscitated by Nathorst[955] for specimens which he names _T. Schenki_, formerly included by Schenk in his species _T. Brauniana_[956]. It bears a close resemblance, in the long linear pinnules with an entire or crenulate margin, to _Dictyophyllum Fuchsi_ described by Zeiller[957] from Tonkin, and it would seem hardly necessary to adopt a distinctive generic designation. The sporangia have a vertical or slightly oblique annulus and the rhizome is similar to that of _Dictyophyllum exile_. The habit of the genus is shown in fig. 284, which represents one of the German Rhaetic species. [Illustration: FIG. 284. _Thaumatopteris Münsteri._ (From a specimen in the Bergakademie, Berlin; ⅓ nat. size.)] _Clathropteris._ _Clathropteris meniscoides_, Brongn. Fig. 285.