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Four species, Arxina parva (Douville, 1930), Arxina cf. schwageri (Silvestri, 1928) A. schwageri (Silvestri, 1928) and Arxina sp. cf. alpina (Douville, 1916) assigned to the newly erected genus Arxina, are recorded from the Middle Eocene of Egypt and Sultanate of Oman. The phylogenetic trend of these species exhibits a progressive increase in the size, a flattening of the test and a general trend of the coalescence of granules which become smaller in size.

The two mica granites of El-Shallal area being emplaced into biotite schists, which underwent high temperature low pressure metamorphism. The two mica granite is peraluminous leucoadamellite to leucogranite in composition, Fe-rich sub-alkaline, with low contents of Ba, Ce and Sm and high contents of Rb, U and K. These facts substantiate the geochemical characteristics of S-type granites. The field observations and petrochemical characteristics are consistent with the derivation of El-Shallal two mica granites from biotite schists. Many of geochemical and mineralogical characteristics of El-Shallal two mica granites are similar to those of fertile Granites Uranifere Français (G.U.F). The average uranium and thorium contents of the two mica granites are relatively high (17 and 32 ppm respectively) and increase during late magmatic stage (72 and 134 ppm respectively) close to basic dykes (chemical traps for U-bearing solutions) compared to the average granitic rocks and exceed the international average content in the crustal rocks. El-Shallal leucogranites may represent the source for uranium occurrences at Um Bogma formation as a result of leaching and remobilization by circulated meteoric water and precipitated simultaneous with and after sedimentation.

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