320 GEOLOGICAL RELATIONS OF THE ROCK SYSTEMS 



Professor Morris in 1836 * under the generic name of Ptilophyllum. Of 

 the ferns, one Tceniopteris (a genus only known in Mesozoic and Cceno- 

 zoic rocks) seems undistinguishable from the T. (Otopteris) Ovalis (L. 

 and H.; from the oolitic shale of Gristhorpe Bay : while the remainder 

 find their nearest analogues, among described species, in those which are 

 of the same general age. To this general result there is one marked 

 exception in the occurrence of two varieties of the peculiar genus Dic- 

 tyopteris (Lmopteris) no specimens of which have as yet been found 

 in rocks of a more modern epoch than the true coal-measures of 

 Europe. 



Of the Pecopteridce one very abundant form is a Gleichenites, a 

 palaeozoic form. Of Cyclopteris (a genus in which the majority of the 

 species are palaeozoic, although its representatives extend upwards into the 

 newer Mesozoic era) we have but one species. Sphenopteris is equally a 

 genus as strongly, if not more strongly, represented among the palasozoic 

 rocks, than among the newer groups. 



The remains of ferns, therefore, are such that the group might be 

 supposed either Palaeozoic or Mesozoic. 



We may pass over the Lycopodiacece as they are not sufficiently 

 characteristic to prove any thing definite. 



Of the Cycadece the genus Cycadites is hitherto only known from 

 formations truly Mesozoic, with the exception of one species (doubtful) 

 from the coal-measures. Pterophyllum, and Palceozamia again are truly 

 Mesozoic genera, while the genus Stangeriles was established by Borne- 

 man for plants found in the Liassic Lettenkohlen Grappe of Thuringia. 



Voltzia, again, is hitherto only known as a Triassic genus, and Br achy 

 phyllum as Jurassic. 



It would seem therefore, from an examination of the general charac- 

 ters of this flora, that it might, without in the least degree straining 

 the evidence, be taken as representative of any period within the great 



* Transactions of Geol. Soc. London 2nd Ser. Vol. V, p. '627. 



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