The geological history of this division of the Pteridophyta is exceedingly meagre, a fact all the more regrettable as it is by no means improbable that in the surviving genus _Isoetes_ we have an isolated type possibly of considerable antiquity and closely akin to such extinct genera as _Pleuromeia_ and _Sigillaria_. If Saporta’s Lower Cretaceous species _Isoetes Choffati[146]_, or more appropriately _Isoetites Choffati_, is correctly determined, it is the oldest fossil member of the family and indeed the most satisfactory among the more than doubtful species described as extinct forms of _Isoetes_. Isoetites. The generic name _Isoetites_ was first used by Münster[147] in the description of a specimen, from the Jurassic lithographic slates of Solenhofen in Bavaria, which he named _Isoetites crociformis_. The specific name was chosen to express a resemblance of the tuberous appearance of the lower part of the imperfectly preserved and indeterminable fossil to a Crocus corm. Impressions of Isoetes-like leaves from the Inferior Oolite of Yorkshire figured by Phillips[148] and afterwards by Lindley[149] as _Solenites Murrayana_ were compared by the latter author with _Isoetes_ and _Pilularia_, but these leaves are now generally assigned to Heer’s gymnospermous genus _Czekanowskia_. An examination of the structure of the epidermal cells of these Jurassic impressions convinced me that they resemble recent coniferous needles more closely than the leaves of any Pteridophyte. The genus _Czekanowskia[150]_ is recognised by several authors as a probable member of the Ginkgoales. _Isoetites Choffati._ Saporta. The late Marquis of Saporta founded this species on two sets of impressions from the Urgonian (Lower Cretaceous) of Portugal which, though not found in actual organic connexion, may possibly be portions of the same plant. Small relatively broad tuberous bodies reaching a breadth of 1 cm. are compared with the short and broad stem of _Isoetes_, which they resemble in bearing numerous appendages radiating from the surface like the roots of the recent species; on the exposed face of the stem occur scattered circular scars representing the position of roots which were detached before fossilisation. Other impressions are identified as the basal portions of sporophylls bearing sporangia: these suggest the expanded base of the fertile leaves of _Isoetes_ with vertically elongated sporangia, some of which have a smooth surface while in others traces of internal structure are exposed; the interior consists of an irregular network with depressions containing carbonised remains of spores.