the greater resemblance between the fertile and vegetative shoots of _Bothrodendron_, as compared with the more pronounced difference in the case of _Lepidodendron_, may be regarded as an argument in favour of recognising _Bothrodendron_ as the more primitive type. Another possible example of a _Bothrodendron_ cone has been described by Nathorst from Spitzbergen as _Lepidostrobus_ _Zeilleri_[649]; this appears to consist of an axis bearing spirally disposed sporangia without any indication of sporophylls. This strobilus may belong to _Bothrodendron tenerrimum_. _Pinakodendron_. The name _Pinakodendron_[650] was instituted by the late Prof. Weiss for a type of stem closely resembling _Bothrodendron_ but differing in the presence of a fine reticulation on the outer bark and in the form of the leaf-scars. Weiss’s genus has been recognised by Kidston in Dumfriesshire but our knowledge of the plant is as yet based solely on a few small specimens. _Omphalophloios_ (_a genus of uncertain systematic position_). Figs. 193, C, 217. This generic name was instituted by White[651] for certain specimens of large stems originally described by Lesquereux from the Coal-Measures of North America as _Lepidodendron mammillatum_ and _L. cyclostigma_. The photograph reproduced in fig. 193, C, for which I am indebted to Dr Kidston[652], represents a specimen described by him from the Upper Coal-Measures of Somerset as _Omphalophloios anglicus_, and identified with _Lepidodendron anglicum_ of Sternberg. The surface of the impression shown in fig. 193, C, is characterised by clearly defined rhomboidal areas or cushions (fig. 217, E) like those of _Lepidodendron_, except in the absence of a median keel, and similar to those on some forms of _Sigillaria Brardi_. A short distance above the centre of each cushion is an oval or subcordate region bounded by a rim-like margin and containing a small oval scar, presumably that of a vascular strand. A triangular elevation which also shows a small pit (Fig. 217, E, _a_) occurs below the oval area. The appearance of the surface-features varies considerably on different parts of a single specimen. Fig. 217, D, represents one of the numerous figures published by White in his detailed account of the American material. Each cushion bears a widely open =V=-shaped ridge, which is described as a leaf-scar; above this is an oval area (2·5 mm. × 1·75 mm.), the surface of which is bounded by a narrow rim. Within the rim is a smaller concave oval region with a small pit near its upper end. [Illustration: FIG. 217. _Omphalophloios._ D. After White. E. After Kidston.]