It is not always easy to distinguish _Todites Williamsoni_ from _Cladophlebis denticulata_, another common Jurassic fern, but in the latter the pinnules are usually longer and relatively narrower and the rachis is more slender (cf. fig. 256, B and 257). Schenk[800] and Raciborski[801] have shown that the sporangia of _Todites_ conform in the absence of a true annulus to those of _Todea_ (fig. 256, G) and _Osmunda_. Nathorst[802] has recently figured a group of spores of _Todites Williamsoni_ in illustration of the use of the treatment of carbonised impressions with nitric acid and potassium chlorate. This species, though widely distributed in Jurassic rocks, is hardly distinguishable from the German Rhaetic fronds figured by Schenk from Bayreuth as _Acrostichites Goeppertianus_[803], or from other fossils referred to an unnecessarily large number of species by Fontaine[804] from Upper Triassic rocks of Virginia[805]. It would seem from the paucity of later records of Osmundaceae that the family reached its zenith in the Jurassic era. When we pass to the later Tertiary and more recent deposits evidence is afforded in regard to the geographical range of _Osmunda regalis_. It has been shown to occur in the Pliocene forest-bed of Norfolk[806] as well as in Palaeolithic and Neolithic deposits[807]. [Illustration: FIG. 257. _Cladophlebis denticulata._ (From a specimen in the British Museum from the Inferior Oolite rocks of Yorkshire. Slightly reduced.)] A fertile frond from the Molteno (Rhaetic) beds of South Africa referred to _Cladophlebis_ (_Todites_) _Roesserti_ (Presl)[808] represents in all probability an Osmundaceous fern closely allied to _Todites Williamsoni_. The same species is described by Zeiller[809] from Rhaetic rocks of Tonkin and very similar types are figured by Leuthardt[810] from Upper Triassic rocks of Basel as _Pecopteris Rutimeyeri_ Heer, and by Fontaine[811] from rocks of the same age in Virginia. _Cladophlebis._ The generic name _Cladophlebis_ was instituted by Brongniart for Mesozoic fern fronds characterised by ultimate segments of linear or more or less falcate form attached to the pinnae by the whole of the base, as in the Palaeozoic genus _Pecopteris_, possessing a midrib strongly marked at the base and dividing towards the distal end of the lamina into finer branches and giving off secondary forked and arched veins at an acute angle. The term is generally restricted to Mesozoic fern fronds which, on account of the absence or imperfection of fertile pinnae, cannot be safely assigned to a particular family. In the case of the species described below, the evidence in regard to systematic position, though not conclusive, is sufficiently strong to justify its inclusion in the Osmundaceae. _Cladophlebis denticulata_ Brongniart. Figs. 256, A; 257, 258. 1828. _Pecopteris denticulata_[812], Brongniart, Prodrome, p. 57; Hist. vég. foss. p. 301, Pl. XCVIII. figs. 1, 2.