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_. [Illustration: 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. Heer[528] proposed to transfer Phillips’ species to the genus _Phyllotheca_, and Schimper[529] preferred the generic term _Schizoneura_. The suggestion for the use of these two names would probably not have been made had the presence of the _Equisetum_ sheaths been recognised.