310 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



included among the various described species of CladopMehis . It need 

 but be remembered how many unrelated modern ferns liave fronds 

 of the Clado'phlebis type, as for example certain species of AlsopMla, 

 Asplenium, Cyathea, Dryoyteris, Gleichenia, Onoclea, Osmunda, 

 Pteris, Poly podium, etc., to cast doubt upon the botanical affinity 

 of Cladoplilehis 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 Aspidieae, or as it is more prop- 

 erly known, Dryopterideae ; and because of this, and also because 

 their actual identity with the modern genus Dryopteris or in fact with 

 any of the modern genera in tliis subfamily is extremely questionable, 

 it has seemed wiser to use the more general name CladopTdehis instead 

 of using Dryopteris where the sterile and fertile fronds have been 

 correlated. 



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

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

 India. The genus appears in force in the Keuper and Khaetic with 

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

 the Jurassic, certain types such as dadopTilehis denticulata apparently 

 becoming world wide in their distribution. For the Lower Cretaceous 

 Saporta has founded a large number of species based upon Portu- 

 guese 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 Cladophlehis, altogether losing sight of variations and changes due 

 to age or to position of the fossils with regard to the frond as a whole, 

 as well as changes due to the direct action of the environment. These 

 species 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 material, and including 

 with it all of the forms recorded from Maryland, w^e have a total of 

 8 species, and these 8 species include remains which were the basis for 

 23 of Fontaine's species and varieties of Cladophlehis, 6 of his species 

 of Dryopteris and 9 of his species of Pecopteris. 



CLADOPHLEBIS ALBERTSII (Dunker) Brongniart. 



Neuropteris albcrtsii Dunker, Monogr. Norddeutsch. Wealdenbildung, 1846, p. 8, 



pi. 7, figs. 6, 6a. 

 Alethopteris albertsii Schimper, Pal. Veg^t, vol. 1, 1869, p. 570. 

 Pecopteris whitbiensis Trautschold, Nouv. Mem. Soc. Nat. Moscou, vol. 13, 1870, 



p. 27, pi. 19, fig. 2. 

 Pteris ? albertsii Heer, Flora foss. Arct., vol. 6, Abth. 2, 1882, p. 29, pi. 16, 



figs. 5, 6; pi. 28, figs. 1-3; pi. 46, figs. 22-24. 

 Pteris albertini Velenovsky, Abh. k. bohm. Ges. Wiss., vol. 2, 1888, p. 15, pi. 4, 



figs. 6-10 (not fig. 5). 

 Cladophlebis albertsii Brongniart, Tableau, 1849, p. 107.— Seward, Wealden 



Flora, pt. 1, 1894, p. 91, pi. 8. 



