146 The Lower Cretaceous Floras of the World 



Africa (Egypt) 



The Nubian sandstone which forms so extensive a part of the surface 

 of the Libyan desert is regarded by De Lapparent as of Albian age/ 

 Petrified woods were described by linger from this area as early as 1843/ 

 and again in 1858.^ Carruthers/ Heer/ and Schenk' have also con- 

 tributed to the subject. Most of the material described by these authors 

 is Upper Cretaceous or later, Zittel, in his exhaustive report on the mate- 

 rials and results of the Eohlf's expedition/ regarding some of the plant 

 horizons as Senonian (Nicolia, Araucarioxylon, etc.) and others Danian 

 {Diospyros, Royena, etc.). 



Considerable uncertainty regarding the exact age of some of the ex- 

 posures still prevails. Recently Seward ^ records the following extremely 

 fragmentary remains from various Nubian sandstone outcrops in Egypt : 



Clathropteris egyptiaca Seward 



Weichselia ? 



Cladophlebis sp. cf. Klukia 



These, if correctly identified, would indicate a Lower Cretaceous age, 

 but the remains are so inconclusive, while the outcrop, according to Dr. 

 Hume of the Egyptian Survey, is probably Upper Cretaceous in age 

 (Campanian), so that the probability is all in favor of the Clathropteris 

 representing a more recent genus of Dipteriacese, and the others of being 

 incorrect identifications, as Professor Seward has already pointed out. 



Gener-^ll Character and Distribution 

 When the sp'ecies recorded from the Potomac Group are added to the 

 foregoing incomplete lists a very considerable flora is recorded from the 



^ De Lapparent, Traite, tome iii, 1906, p. 1368. 

 ^ Unger in Endlicher's Genera Plantarum, Suppl. ii, 1843, p. 102. 

 =* linger, Sitzungs. K. Akad. Wiss., Wien, Bd. xxxiii, 1858, pp. 209-233, pis. 

 i-iii. 



* Carruthers, Geol. Mag., vol. vii, 1870, pp. 306-310, pi. xiv. 



'Hear, Neue Denks. Schweiz. Gesell. Naturwiss., Bd. xxvii, Abth. i. No. 2, 

 1876, pp. 11, pi. i. 



* Schenk, Palseontographica, Band xxx, 1883. 

 ' Palseontographica, Band xxx, 1883. 



* Seward, Geol. Mag., dec. v, vol. iv, 1907, pp. 253-257, tf. 1-3. 



