THE GEOLOGY OE EGYPT. 401 



been fully described by Zittel (34), who finds that it con- 

 sists of three main divisions, viz. (in descending order)- 



3. White well-bedded limestone or earthy chalk. 

 2. Greenish and ash-grey shaly clays. 

 1. Beds with Exogyra Overzvegi. 



The Overwegi beds, which rest with perfect conformity 

 upon the Nubian Sandstone, are some 130 m. thick. In the 

 lowest part of the series the predominant rock is a brown 

 iron-shot sandstone, in which fish teeth occur in great 

 numbers, and fossil wood is also occasionally found. The 

 teeth belong to the genera Otodus, Lamna, Corax (C. 

 prist odontus), etc. The middle beds are for the most 

 part variegated clays, with banks of sandstone, marl, and 

 limestone ; and it is here that the characteristic fossils of 

 the series, such as Exogyra Ovcnvegi and Inoceramus 

 Cripsi var. regularis, are most abundant. The upper beds, 

 which are chiefly laminated clays, are relatively poor in 

 fossils. 



The shaly clays which overlie the Overwegi beds are 

 but little different in appearance from those which are 

 found in the Overwegi series itself. Besides gypsum and 

 rock-salt they contain also brown iron-ore, and iron pyrites 

 superficially oxidised Fossils are not abundant except in 

 certain beds, and are fairly distinct from those of the Overwegi 

 stage. Among them are Nautilus danicus, JV. desertorum, 

 etc. 



The highest beds of the Cretaceous consist of well- 

 bedded chalky limestone, often somewhat marly at its 

 base. It joins the top of the escarpment which rises on 

 the north side of the Dakhla oasis, while in the Kharga 

 oasis it is itself capped by the Eocene limestones. In the 

 oasis of Farafra it shows all the characters of a true chalk, 

 and consists almost entirely of Coccoliths and Foraminifera. 

 Among the chief fossils which have been found in it are 

 Ananckytes ovata, Gryphea cf. vesicular is, Pec ten Fara- 

 frensis, etc., and numerous fish teeth. 



Many of the species which occur in the Egyptian 

 Cretaceous are new ; but the presence in the lower beds, 



