XXIX.–On Rhetinangium arberi, a new genus of Cycadofilices from the Calciferous Sandstone Series.

Abstract

During the past few years probably no group of fossil plants has received more attention from palæobotanists than that of the Pteridospermeæ. Many fern-like impressions, derived from Carboniferous rocks, have proved to be members of this division of the vegetable kingdom; while many more may ultimately be removed from the Filicales and included in the Pteridospermeæ. Specimens, however, in which the internal structure is preserved, may, as a rule, be correctly referred to their respective class, but among those included in the latter group there is considerable diversity of organisation, and recently described genera have tended to increase the diversity of type rather than to indicate relationships among the forms already known.