218 MR R. KIDSTON AND MR D. T. GWYNNE-A^AUGHAN ON 



character is of too general occurrence to be accepted as indicating generic identity 

 between the fern stems in question. The genus Tliamnopteris, as it will be employed 

 by us, when we come to describe the specimen in detail, will be one which derives its 

 essentia] characters from the anatomy of the stem. We take this liberty of altering 

 the generic characters on the strength of the fact that the stem we hope to describe, 

 though not actually the individual to which Brongniart's remarks refer, is one of 

 two which were figured and described by Eichwald as belonging to his Sphallopteris 

 Schlechtendalii. 



It is similar considerations which have prompted us to remove the Chelepteris 

 gracilis, Eichwald, from that genus and to place it in the new genus Zalesskya. This 

 stem has not only lost its mantle of leaf-bases, but is also partially decorticated, so its 

 outer surface is unknown. The whole of the characters of the genus Chelepteris, Corda, 

 are derived from external features, and possibly the specimens placed in Chelepteris 

 by Corda may show their outer surface ; but be this as it may, the genus Zalesskya is 

 founded on characters derived entirely from its interna] organisation — an organisation 

 which one has no right to infer was possessed by the original types of the genus Chelepteris. 



It is difficult and probably useless to attempt to define the relationship of the plants 

 placed in Chelepteris, Corda, to the Chelepteris (Zalesskya) gracilis of Eichwald ; but 

 we are of opinion that they are probably generically distinct, though it is impossible 

 to determine this point satisfactorily. 



The genera Chelepteris, Corda (non Eichwald), and Sphallop)teris, Corda (emend.), are 

 placed by Brongniart alongside of Protopteris, which is compared with the Dicksonise, 

 though he points out that the same type of leaf-trace occurs in the Osmundacese and 

 other ferns. 



Though the genus Protopteris, Presl,* may be Cyatheaceous, we are clearly of opinion 

 that the fern stems described by Eichwald under the names of Chelepteris and 

 Sphallopteris (without expressing any opinion on the fossils placed in these genera by 

 Corda) are Osmundaceous, and, along with Zalesskya and Anomorrhcea, must be 

 removed from the Protopteridese. 



Schimper, in his Traite d. paleont. veget.,\ treats Thamnopteris, Anomorrhcea, 

 Chelepteris, and Bathypteris as distinct genera, hutinZAtteYsHandbuchd.Pcdaeontologie]. 

 he unites Anomorrhcea and Bathypteris with TJiamnopteris, remarking that there are 

 no grounds for placing these fern stems in different genera as has been done, as the 

 outer surfaces of all show the same characters ; and had not one the structure of the 

 specimens to direct them, this appears to us as the wisest way of treating the fossils, 

 though, as will be seen later on, we still keep these genera separate, but from an 

 altogether different class of characters than those observable on their outer surfaces. 



We have thought it necessary to give this review of the literature of the subject, to 

 show the opinions held by the various botanists who have written about these fossil fern 



* PKESL in Sternberg. Vers., vol. ii., fasc. vii.-viii., p. 169, 1838. 



+ Vol. i., pp. 701-3, 1869. 



I Schimi'ek in Zittel, Handh. d. Palaeont., II. Abth., Palaeophylologie, p. 145, 1879. 



