The stem shown in fig. 62 appears to be a portion of a shoot of E. Beani not far from its apical region. From the lower nodes there extend clearly marked and regular lines or slight grooves tapering gradually towards the next higher node; these are no doubt the impressions of segments of leaf-sheaths. The sheaths themselves have been detached and only their impressions remain. The flattened bands at the node of the stem in fig. 60, and shown also in fig. 61, mark the place of attachment of the leaf-sheaths. On some of these nodal bands one is able to recognise small scars which are most likely the casts of outgoing leaf-trace bundles.
Some of the internal casts of this species are marked by numerous closely arranged longitudinal lines, which are probably the impressions of the inner face of a central woody cylinder. In the smaller specimen shown in fig. 62 we have the apical portion of a shoot in which the uppermost internodes are in an unexpanded condition.
Fig. 62. Equisetites Beani (Bunb.). From a specimen in the Scarborough Museum. Very slightly reduced.
It is impossible to give a satisfactory diagnosis of this species without better material. The plant is characterised chiefly by the great breadth of the stem, and by the possession of leaf-sheaths consisting of numerous long and narrow segments. Equisetites Beani must have almost equalled in size the Triassic species, E. arenaceus, described above.
7. Equisetites lateralis Phill. Figs. 58, F, 63, and 64.
This species is described at some length as affording a useful illustration of the misleading character of certain features which are entirely due to methods of preservation. The specific name was proposed by Phillips in his first edition of the Geology of the Yorkshire Coast for some very imperfect stems from the Lower Oolite rocks near Whitby[524]. The choice of the term lateralis illustrates a misconception; it was given to the plant in the belief that certain characteristic wheel-like marks on the stems were the scars of branches. Lindley and Hutton[525] figured a specimen of this species in their Fossil Flora, and quoted a remark by “Mr Williamson junior” (afterwards Prof. Williamson) that the so-called scars often occur as isolated discs in the neighbourhood of the stems. Bunbury[526] described an example of the same species with narrow spreading leaves like those of a Palaeozoic Asterophyllites, and proposed this generic name as more appropriate than Equisetites. In all probability the example shown in fig. 63 is that which Bunbury described. It is certainly the same as one figured by Zigno[527] as Calamites lateralis in his Flora fossilis formationis Oolithicae.
Fig. 63. Equisetites lateralis Phill. From a specimen in the British Museum. Slightly reduced.
This specimen illustrates a further misconception in the diagnosis of the species. The long linear appendages spreading from the nodes are, I believe, slender branches and not leaves; they have not the form of delicate filmy markings on the rock face, but are comparatively thick and almost woody in appearance. The true leaves are distinctly indicated at the nodes, and exhibit the ordinary features of toothed sheaths.