The term Botryopterideae, first used by Renault, has been applied to a group of Palaeozoic ferns ranging from the Lower Carboniferous to the Permian and containing several genera, the distinguishing features of which are supplied by the anatomical structure of the stems or, in many cases, by that of the petiolar vascular strand. Scott[1109] subdivides the Botryopterideae into the Botryopteris and the Zygopteris sections. In an admirable monograph recently published by Paul Bertrand[1110] considerable changes are proposed in current nomenclature; he substitutes the name Inversicatenales for Botryopterideae, a designation, which as Scott remarks, is “probably too technical to command general acceptance.” A more serious criticism is that the name Inversicatenales has reference to a character (the inverse curvature of the leaf-trace in relation to the axis of the stem) which is by no means universal in the group[1111]. In the following account, necessarily incomplete, the generic terminology of Bertrand is adopted, but this decision does not carry with it any obligation to accept the name Inversicatenales. We may speak of the types of Palaeozoic ferns dealt with in the following pages as members of a group differing in many respects from any existing genera of the Filicales, and exhibiting the characteristics associated with generalised plants. Williamson, as early as 1883, spoke of Renault’s Botryopterideae as comprising “altogether extinct and generalised” types[1112]. For these generalised Palaeozoic ferns I propose to use the name Coenopterideae[1113]. This term may be adopted in a wider sense than Renault’s name Botryopterideae. The name Primofilices proposed by Arber[1114] might be employed, but the implication which it carries is an argument against its adoption. We have not yet reached a stage in the investigation of extinct types at which we are able to recognise what are actually primary or primitive ferns. The search for origins will continue; as new discoveries are made our point of view shifts and the primitive type of to-day may to-morrow have to take a higher place. The epithet primitive or primary is in reality provisional: to adopt such a name as Primofilices suggests a finality which has not been, or is likely to be, achieved. The true ancestral type—the _Urform_—which we strive to discover eludes the pursuer like a will-o’-the-wisp.