A few examples of _Phyllotheca deliquescens_ have been described by Schmalhausen in which a branch bears clusters of sporangiophores, alternating with verticils of sterile bracts. The sporangiophores appear to have the form of stalked peltate appendages bearing sporangia, very similar to the sporangiophores of _Equisetum_. Solms-Laubach[561] has examined the best of Schmalhausen’s specimens, and a carefully drawn figure of one of the fertile branches is given in his _Fossil Botany_. The significance of this manner of occurrence of sporangiophores and whorls of sterile bracts on the fertile branch will be better understood after a description of the strobilus of _Calamites_. In _Phyllotheca_ the sporangiophores appear to have been given off in whorls, which were separated from one another by whorls of sterile bracts, whereas in _Equisetum_ there are no sterile appendages associated with the sporangiophores of the strobilus, with the exception of the annulus at the base of the cone. Heer[562] first drew attention to the fact that in _Phyllotheca_ we have a form of strobilus or fertile shoot to a certain extent intermediate in character between _Equisetum_ and _Calamites_. In abnormal fertile shoots of _Equisetum_, sporophylls occasionally occur above and below a sterile leaf-sheath. Potonié[563] has figured such an example in which an apical strobilus is succeeded at a lower level by a sterile leaf-sheath, and this again by a second cluster of sporophylls. As Potonié points out, this alternation of fertile and sterile members affords an interesting resemblance between _Phyllotheca_ and _Equisetum_. It suggests a partial reversion towards the Calamitean type of strobilus. 2. _Phyllotheca Brongniarti_ Zigno. Fig. 68, A. This species of _Phyllotheca_ from the Lower Oolite rocks of Italy is known only in the form of sterile branches. The leaves are fused basally into an open cup-like sheath which is dissected into several spreading and incurved linear segments. The internodes are striated longitudinally; they are about 2 mm. in diameter and 10 mm. in length. The specimen represented in fig. 68, A, was originally described by the Italian palaeobotanist Zigno[564]; it serves to illustrate the points of difference between this genus and the ordinary _Equisetum_. The open and spreading sheaths clasping the nodes and the erect solitary branches give the plant a distinctive appearance. [Illustration: FIG. 68. A. _Phyllotheca Brongniarti_, Zigno. Nat. size. (After Zigno.) B. _Calamocladus frondosus_, Grand’Eury. (After Grand’Eury.) Slightly enlarged. C. _Phyllotheca indica_, Bunb. Part of a leaf-sheath. From a specimen in the Museum of the Geological Society. Slightly enlarged.] 3. _Phyllotheca indica_ Bunb. and _P. australis_ Brongn. Fig. 68, C.