_Ceratozamia._ The fronds bear a fairly close resemblance to those of _Macrozamia_: in _Ceratozamia mexicana_ the linear pinnae reach a length of over 30 cm. and a breadth of 2–3 cm.; the lamina tapers to a narrow apex and is more abruptly contracted at the base (fig. 387, H). The veins in _Ceratozamia_ are sub-parallel and dichotomy occurs up to the middle of the lamina[49]. A striking feature is the occurrence of two opposite stipule-like projections a short distance above the base of the petiole. _Macrozamia._ A noteworthy feature in some species is the attachment of the linear pinnae along the middle line of the rachis (fig. 387, C); in others (fig. 387, B) the leaflets are attached laterally and may have a basal callosity. The parallel veins, which branch dichotomously near the base of the lamina, are often much more prominent on the lower than on the upper face. In _M. heteromera_[50] (fig. 396, F, F′) the narrow pinnae are deeply forked and strongly revolute. The spirally twisted rachis of _M. spiralis_, _M. heteromera_, etc., is a striking feature recalling the Rhaetic fern _Camptopteris spiralis_ Nath[51]. _Dioon._ The arrangement of the linear pinnae of _D. edule_ (fig. 386, B), _D. spinulosum_, and _D. Purpusii_[52] forms a ready means of distinguishing the fronds of this genus: the pinnae, often contiguous and at right-angles to the rachis, are attached in a lateral groove by an expanded and slightly decurrent base. The difference between the lower and upper face of a frond (fig. 387, E, F) affords a good illustration of a common source of error in the identification of fossil specimens. The leaflets of _D. spinulosum_, which except in their spinous margin are very similar to those of _D. edule_, may reach a length of 15 cm. and a breadth of 8 mm. The parallel veins are unbranched[53]. _Microcycas[54]._ The pinnae of this genus, very like those of the Wealden species _Zamites Buchianus_, reach a length of 20 cm. and a breadth of 8 mm.: on falling they leave oblong scars resembling those on the rachis of _Encephalartos_. _Stangeria._ This genus is particularly interesting because of its fern-like habit and venation. The large fronds of _S. paradoxa_[55] bear broadly linear acuminate pinnae with entire, unevenly lobed, serrate, or pinnatifid margins. Some leaflets are so deeply dissected as almost to justify the appellation pinnate. Both entire and dissected leaflets may occur on one frond and the lower ones may be stalked while the upper pinnae are sessile. The venation agrees closely with that of the genus _Taeniopteris_[56].