A. _Diplolabis forensis._ B. _Botryopteris forensis._ C, D. _Corynepteris coralloides._ E. _Schizopteris_ (_Etapteris_) _pinnata_. (A, B, after Renault; C, D, after Zeiller; E, after Renault and Zeiller.)] The vascular strand of the rachis of _Zygopteris primaria_ (fig. 308, D) is simpler than that of most of the Zygoptereae and exhibits a close resemblance to the type of strand described by Renault as _Diplolabis_ (fig. 308, C). _Diplolabis._ Renault[1136] instituted this genus for two species from the Culm beds and Coal-Measures of France based on the structure of the petioles. The stems are unknown. The main rachis has a stele similar to that of _Zygopteris primaria_, but distinguished by its greater similarity, in transverse section, to an =X= rather than to the letter =H=: the long transverse bar in _Zygopteris_ is here much reduced in size. The petiole of _Diplolabis forensis_[1137] Ren. (fig. 308, C) has a diameter of 1·5–2 cm. From the antennae a pair of small bundles is given off alternately from the right and left side, as in _Zygopteris_; the members of each pair coalesce after leaving the antennae and then separate to pass into the lateral branches of the frond. The position of the protoxylem and the formation of the lateral xylem strands previous to their separation are shown in fig. 308, C. On the side of the vascular strand shown in fig. C, 2, the two lateral extensions of the antennae are converging towards one another previous to their separation and subsequent union. The ovoid sporangia occur in groups of three to six and are coalescent below with a central receptacle; they have no annulus, but the cells on the side next the receptacle are smaller than those on the external wall (fig. 309, A). The synangial form of the sorus suggests comparison with Marattiaceae. The species described by Renault from the Culm of Esnost is regarded by P. Bertrand as identical with that described by Solms, from the Culm of Falkenberg, as _Zygopteris Roemeri_[1138]. _Diplolabis_ is compared by P. Bertrand with _Metaclepsydropsis_, the generic name given to the Lower Carboniferous petiole described by Williamson as _Rachiopteris duplex_[1139].