242 Systematic Paleontology 



his. It need but be remembered how many unrelated modern ferns have 

 fronds of the Cladophlebis type, as, for example, certain species of Al- 

 sophila, Asplenium, Cyathea, Dryopteris, Gleichenia, Onoclea, Osmunda, 

 Polypodium, Pteris, etc., to cast doubt upon the botanical affinity of 

 Cladophlebis species unless these are attested by a considerable body 

 of evidence. It is believed, however, that the Potomac species are all 

 to be included in the subfamily Dryopteridese, and because of this and also 

 because their actual identity with the modern genus DryopteriSj or, in 

 fact, with any of the modern genera in this subfamily is extremely ques- 

 tionable, it has seemed wiser to use the more general name CladopJilebis 

 instead of using Dryopteris, where the sterile and fertile fronds have 

 been correlated. Possibly in the end a new generic name, such as 

 Aspidiopteris, will prove to be the most satisfactory solution of the 

 question. 



A large number of species of CladopJilehis have been described, two 

 species, according to Arber, occurring in the Penno-Carboniferous of 

 India. The genus appears in force in the Keuper and Eha^tic, with more 

 than a dozen recorded species. Over a score are recorded during the 

 Jurassic, certain types, such as CladopJilehis denticulata, apparently be- 

 coming world wide in their distribution. For the Lower Cretaceous Sa- 

 porta has founded a large number of species based upon Portuguese 

 material, and Fontaine has instituted a still larger number of American 

 species. From the Potomac beds of Maryland and Virginia the latter 

 author recorded 23 different species, besides several ^varieties of Clado- 

 pJilehis, altogether losing sight of variations and changes due to age, posi- 

 tion of the fossils with regard to the frond as a whole, and changes due 

 to the direct action of the environment. These were often based upon 

 such insufficient material that it becomes almost impossible to deal with 

 them with any degree of assurance. In considering all of the more 

 representative matesial and including with it all of the forms recorded 

 from Maryland, we have a total of eight species, and these eight species 

 include remains which were the basis for twenty-three of Fontaine's 

 species and varieties of CladopJilehis, six of his species of Dryopteris, 

 and nine of his species of Pecopteris. 



