In the _Antediluvian Phytology_, Artis[448] figured a fossil from the Carboniferous sandstones of Yorkshire which he called _Euphorbites vulgaris_ on account of a superficial resemblance to the stems of existing succulent Euphorbias. Rhode[449] also compared Sigillarian stems with those of recent _Cacti_. The specimen described by Artis is characterised by regular vertical and slightly convex ribs bearing rows of leaf-scars in spiral series, like those on the cushions of _Lepidodendron_. A few years earlier Brongniart[450] had instituted the genus _Sigillaria_[451] for plants with ribbed but not jointed stems bearing “disc-like impressions” (leaf-scars) disposed in quincunx; the type-species named by the author of the genus _Sigillaria scutellata_ is identical, as Kidston[452] points out, with _Euphorbites vulgaris_ of Artis and with the plant afterwards figured by Brongniart as _S. pachyderma_[453]. Brongniart in 1822 figured another type of stem characterised by the absence of ribs and by prominent spirally arranged cushions bearing relatively large leaf-scars like the upper part of the specimen shown in fig. 203; this he named _Clathraria Brardii_, a well-known and widely distributed Carboniferous and Permian species now spoken of as _Sigillaria Brardi_ (figs. 196, A–C; 203). A third type of stem figured by Brongniart as _Syringodendron striatum_[454] agrees with _Sigillaria scutellata_ in having ribs, but differs in the substitution of narrow oval ridges or depressions for leaf-scars; this is now recognised as a partially decorticated _Sigillaria_, in which the vascular bundle of each leaf is represented by a narrow ridge or depression. The name _Syringodendron_, originally used by Sternberg, is conveniently applied to certain forms of Sigillarian stems which have lost their superficial tissues. A fourth generic name, _Favularia_, was instituted by Sternberg[455] for Sigillarian stems with ribs covered with contiguous leaf-scars of hexagonal form and prominent lateral angles (fig. 193, A; fig. 200, G). [Illustration: FIG. 193. A. _Sigillaria elegans_ Brongn. B. _Sigillaria rugosa_ Brongn. Middle Coal-Measures. C. _Omphalophloios anglicus_ Kidst. Barnsley. D. _Sigillaria elegans_ Brongn. E. _Sigillaria tessellata_ Brongn. (A, B, C, E, about ¾ nat. size. Dr Kidston’s Collection.)] The generic or sub-generic title _Rhytidolepis_, also instituted by Sternberg, is applied to ribbed Sigillarian stems such as _S. scutellata_, _S. rugosa_ (fig. 193, B), _S. mammillaris_ (fig. 195), or _S. laevigata_ (fig. 196, D). Goldenberg[456] proposed the name _Leiodermaria_ for smooth Sigillarian stems with leaf-scars not in contact with one another (fig. 196, C).