Clathropteris.
Clathropteris meniscoides, Brongn. Fig. 285.
Clathropteris, founded by Brongniart[958] for Rhaetic specimens from Scania, agrees very closely with some species of Dictyophyllum, but in view of the more rectangular form of the venation-meshes it is convenient to retain both names. The type-species was originally named Filicites meniscoides[959] and afterwards transferred to Clathropteris. An examination of Brongniart’s specimens has convinced Nathorst of the specific identity of C. meniscoides and C. platyphylla. The Tonkin leaves described by Zeiller[960] under the latter name should, therefore, be included in C. meniscoides, which may be thus defined:
The petiolate frond is characterised by an equal dichotomy of the rachis, as in Dictyophyllum; each branch bore 5–15 pinnae, disposed en éventail, reaching a length of 20–30 cm. and fused basally as in D. Nathorsti Zeill. Pinnae linear lanceolate, slightly contracted at the lower end and gradually tapered distally. The lamina, 3–14 cm. broad, is characterised by obtusely pointed marginal lobes. From the midrib of each pinna lateral veins are given off at a wide angle, and adjacent veins are connected by a series of branches which divide the lamina into a regular reticulum of rectangular and polygonal meshes ([fig. 285]). The sori are abundant and contain 5–12 sporangia like those of Dictyophyllum.
Fig. 285. Clathropteris meniscoides. From Rhaetic rocks near Erlangen. [M.S.]
Fig. 286. Clathropteris egyptiaca. (Nat. size.) a, b, pieces of main ribs in grooves.
What is probably the rhizome of this species has been described by Nathorst (Rhizomopteris cruciata); it is similar to that of Dictyophyllum, but the leaf-scars are more widely separated. This species occurs in Upper Triassic, Rhaetic or Lower Jurassic rocks of Scania, France, Germany, Switzerland, Bornholm, North America, China, Tonkin, and Persia and is represented by fragments in the Rhaetic beds of Bristol[961].