On the broader stems, such as that of fig. 67, we have clearly marked narrow grooves and broader and slightly convex ridges, which present an appearance identical with that of some Calamitean stems. In the specimen figured by Bunbury[568] in his Pl. X, fig. 6, there is a circular depression on the line of the node which represents the impression of the basal end of a branch; on the edges of the node there are indications of two other lateral branches. The nature of this stem-cast points umnistakeably to a woody stem like that of _Calamites_. The precise meaning of the ridges and grooves on the cast is described in the Chapter dealing with Calamitean plants. [Sidenote: CALAMOCLADUS.] Grand’Eury[569] in his monograph on the coal-basin of Gard, has recently described under the name of _Calamocladus frondosus_ what he believes to be the leaf-bearing axes of a Calamitean plant. The thicker branches are almost exactly identical in appearance with the broader specimens of _Phyllotheca_. The finer branches of _Calamocladus_ bear cup-like leaf-sheaths which are divided into long and narrow recurved segments (fig. 67, B), precisely as in _Phyllotheca_. These comparisons lead one to the opinion that the _Phyllotheca_ of Australia and India may be a close ally of the Permo-Carboniferous Calamitean plants. The form of the leaf-whorls of _Annularia_ (Calamarian leaf-bearing branches) and of _Calamocladus_ is of the same type as in _Phyllotheca_; the character of the medullary casts is also the same. The nature of the fertile shoot of _Phyllotheca_ described by Schmalhausen from Siberia, with its alternating whorls of sterile and fertile leaves, is another point of agreement between this genus and Calamitean plants. An Equisetaceous species has been described from the Newcastle Coal-Measures of Australia by Etheridge[570] in which there are two forms of leaves, some of which closely resemble those of _Phyllotheca indica_, while others are compared with the sterile bracts of _Cingularia_, a Calamitean genus instituted by Weiss[571]. When we turn to other recorded forms of _Phyllotheca_ many of them appear on examination to have been placed in this genus on unsatisfactory grounds. Heer figures several stem fragments from the Jurassic rocks of Siberia as _P. Sibirica_ Heer[572], and it was the resemblance between this form and the English _Equisetites lateralis_ which led to the substitution of _Phyllotheca_ for _Equisetites_ in the latter species. Without examining Heer’s material it is impossible to criticise his conclusions with any completeness, but several of his specimens, appear to possess leaf-sheaths more like those of _Equisetum_ than of _Phyllotheca_.