Bertrand compares the stele of _S. elongata_ with that of the type of _Lepidodendron_ represented by the Burntisland species named by Williamson _L. brevifolium_ (fig. 186) and now usually referred to _L. Veltheimianum_; the chief distinguishing features are the greater prominence in the French species of the surface-ridges or teeth of the primary xylem, a feature which occurs in _L. Wünschianum_, and the detachment of the leaf-traces from the bottom of each sinus (fig. 202, C, _lt_) instead of from the sides of the sinus. It is, however, not clear how far this latter distinction is a real one; in _Lepidodendron Wünschianum_ the leaf-traces appear to arise, as in _Sigillaria_, from the middle of each sinus. Other types of ribbed Sigillaria stems have been briefly described by Scott[529], Kidston[530], and more recently, by Arber and Thomas[531]. The specimen described by Scott agrees in the main with _S. elegans_ of Kidston and with _S. elongata_ of Bertrand. Kidston’s sections of _S. scutellata_ show a continuous primary xylem cylinder with a slightly and irregularly crenulate outer margin. It would seem that one important diagnostic character in Sigillarian stems is afforded by the degree and form of the crenulations on the outer surface of the primary xylem. _S. scutellata_ has been described also by Arber and Thomas; these authors were the first to demonstrate the presence of a ligule and ligular pit on the leaf-base in a petrified stem, and they also contribute the important fact that the leaf-traces in passing through the phelloderm bifurcate and enter the leaf as two distinct vascular strands. This double bundle has been referred to in the description of Sigillaria leaves. (Page 214.)