In erratic blocks of sandstone, found on the Disco shore of the Waigat, have been detected a Sigillaria and a species of either Pecopterisor Gleichenia, perhaps of this age; and probably much of the extreme northern coast of Ellesmere Land, and therefore, in all likelihood, the opposite Greenland shore, contains a clearly developed Carboniferous Limestone fauna, identical with that so widely distributed over the North American continent, and referable also to British and Spitsbergen species.
- These forms have a horizontal rhizome, from which simply pinnate leaves arise in Platyzoma, while Gleichenia bears compound pinnate leaves with continued apical growth.
The rhizome usually has a solid central cylinder in Gleichenia, while that of Platyzoma is tubular.
Each has an almost horizontal annulus resembling that of Gleichenia, but the dehiscence is lateral.
These curious appendages (Aphlebiae), at first regarded as parasitic growths, have been compared with the feathery outgrowths which occur on the rachis in the Cyatheaceous genus Hemitelia, and with the 'anomalous pinnules found in certain species of Gleichenia, at the points of bifurcation of the frond.
The stem has a single stele, resembling in general primary structure that of one of the simpler species of Gleichenia; there is no pith, the wood extending to the centre of the stele.
The dichotomously-branched fronds, of the type represented by several recent species of Gleichenia, e.g.
- MacClin- sented by Gleichenia, Lygodium and Chryso- kia trinervata.