Certain sections exhibiting this type of structure were described by Binney in 1872 as _Halonia regularis_[328] on evidence supplied by Mr Dawes, who stated that they were cut from a specimen bearing Halonia tubercles. The section represented in fig. 172 is no doubt from an Halonia axis. In 1890 Cash and Lomax[329] stated that they had in their possession a stem of the _L. fuliginosum_ type with the external features of _Lepidophloios_; this identification has been confirmed by Kidston[330] and Weiss[331]. It is, however, equally clear that certain species with the elongated leaf-cushions of _Lepidodendron_ must be included among examples of shoots with the anatomical characters of _L. fuliginosum_. [Illustration: FIG. 173. _Lepidodendron obovatum._ (From a specimen lent by Dr D. H. Scott.)] Dr Scott[332] published in 1906 a short account of the structure of a specimen from the Lower Coal-Measures of Lancashire, the external features of which were identified by Kidston with those of _Lepidodendron obovatum_ Sternb. Dr Scott generously allowed me to have drawings made from his specimen; these are reproduced in fig. 173. The form of the leaf-cushion is by no means perfect; there is a well-marked median ridge, and the small circular scar near the upper end of some of the cushions may represent the ligular cavity. At the base of the leaf-cushions a cortical meristem has produced a zone of secondary cortex; at _c_ a second meristem is seen in the outer cortex: the dark dots in the cortex mark the positions of leaf-trace bundles. The inner cortex, _d_, is a more compact tissue surrounding the imperfectly preserved secretory zone. From the medullated stele a lateral branch, _b_, is being given off; its crescentic form becoming changed to circular as it passes nearer to the surface. [Illustration: FIG. 174. _Lepidodendron aculeatum._ (Cambridge Botany School.)] [Illustration: FIG. 175. _Lepidodendron aculeatum._ (Cambridge Botany School.)] A type of _Lepidodendron_, _L. Hickii_, founded on anatomical characters by Mr Watson[333], is believed by him to possess leaf-cushions like those of _L. obovatum_; if this is so, it is interesting, as he points out, to find two distinct anatomical types associated with one species. Watson thinks it probable that the “species” _L. obovatum_ includes at least two widely different species. This merely emphasizes the importance of correlating structure and external characters as far as available data permit. [Illustration: FIG. 176. _Lepidodendron aculeatum._ (Cambridge Botany School.)]