4 02 SCIENCE PROGRESS. 



of the very characteristic Exogyra Overwegi, suggests that 

 the whole series must belong to the Upper Senonian, for in 

 Tripoli Exogyra Overwegi is associated with Ostrea larva. 

 Others of the common fossils, such as Corax pristodontus, 

 Nautilus danicus, etc., are also Senonian forms, and the 

 whole fossiliferous Cretaceous of Upper Egypt is cor- 

 related by Zittel with the Upper Senonian or Danian. This 

 view is further supported by the fact that there is no 

 break between the chalky beds at the top of the series and 

 the nummulitic rocks above. 



The floor of the Baharia oasis, which lies some distance 

 north of the great belt of oases, is formed of sandstones, 

 marls, etc. They present a considerable resemblance to 

 the lower part of the Overwegi stage, but are succeeded by 

 nummulitic limestone at so short an interval as to pre- 

 clude the possibility of the presence of the higher Cretaceous 

 beds except in a very attenuated form; and hence Zittel was 

 forced to the conclusion that they must be of Tertiary age. 

 Lyons, however, has since discovered Exogyra Overwegi in 

 these beds, and thus shown them to be Cretaceous (16). 



As yet there is no proof on the west side of the Nile 

 of the existence of any Cretaceous rocks older than 

 the Senonian. But in the Arabian Desert east of that 

 river the Senonian is underlaid by other beds containing 

 a rich and varied Cenomanian fauna. 



Near the Monastery of St. Paul, south of the Wadi 

 Araba, Schweinfurth finds a reddish-brown sandstone rest- 

 ing directly upon the crystalline rocks. This is succeeded 

 by an alternation of marly and calcareous beds in which 

 Hcmiaster cubicus occurs in profusion. Other common 

 fossils are Sphcerulites Schiveiufiirthi, Exogyra Africana, 

 Plicatula Fourneli, Ammonites Mantelli, etc., and the 

 whole assemblage can be matched in the Cenomanian 

 deposits of Algeria, Calabria, and other Mediterranean 

 districts. 



In some localities these beds are immediately succeeded 

 by a white chalky limestone ; but in others, for instance, at 

 the Monastery of Saint Antony in the Wadi Araba, there 

 is an intervening series of variegated marls with inter- 



