IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 193 



usually constitutes about one third of the test ; its curved, depressed, dorsal sutures, 

 and radial strongly depressed ventral ones ; its large, crescentic aperture ; and its 

 granular spinose surface. 



The species is believed to have evolved from Globorotalia angulata angulata 

 (White) in Upper Paleocene time by the increase in the surface rugosity, in the size of 

 test and in the rate of chamber growth. All transitional stages between these two 

 species were recorded in the lower part of the Upper Paleocene G. velascoensis Zone 

 of the Esna-Idfu region. On the other hand, G. aequo, is believed to have evolved 

 into G. loeblichi sp. nov. by a reduction in the size of test and in the surface rugosity ; 

 by the development of a distinct, finely beaded keel, a delicately papillose surface and 

 a narrower umbilicus. 



Hypotype. P.45592. 



Horizon and locality. Figured specimen, from Sample No. 55, Gebel Owaina 

 section. 



Stratigraphical range. The species was first recorded from the Paleocene 

 Soldado formation of Trinidad which was described by Cushman & Renz (1942) as 

 " Eocene, Midway, Soldado formation ". 



Bolli (19576) and Loeblich & Tappan (1957a) reported this species from the Upper 

 Paleocene-Lower Eocene of the Lizard Springs formation of Trinidad, and of the 

 Gulf and Atlantic Coastal plains of the U.S.A. respectively. 



All reliable references show that G. aequa is an excellent index fossil for the Upper 

 Paleocene in most parts of the world. 



In the Esna-Idfu region, Globorotalia aequa floods the upper part of the G. velasco- 

 ensis Zone, characterizing together with G. esnaensis the G. aequa/G. esnaensis 

 Subzone, of uppermost Paleocene age. It crosses the Paleocene-Lower Eocene 

 boundary and occurs as a rare form with a much smaller test and a rougher surface in 

 the overlying G. wilcoxeniss Zone. 



Globorotalia africana sp. nov. 



(PI. 23, figs. 4a-c) 



Diagnosis. A Globorotalia with small, concavo-convex, compressed test ; spinose 

 surface ; small, globular, raised early chambers and compressed lenticular later ones ; 

 very large last chamber ; acute axial periphery and partially developed pseudo-keel. 



Description. Test small, concavo-convex, compressed and coiled in a low trocho- 

 spire ; dorsal side gently convex with the early chambers slightly raised above the 

 circumambient last whorl ; ventral side gently concave although the chambers are 

 inflated ; equatorial periphery ovoid, elongate, distinctly lobate and spinose ; axial 

 periphery acute with a partially developed pseudo-keel on the last chamber ; on the 

 dorsal side the chambers are 16, arranged in 3 dextrally coiled whorls ; the initial 

 chambers increase slowly in size, are extremely small, globular, inflated, almost 

 indistinct, and are followed by relatively larger, globular, inflated chambers which 

 increase moderately in size ; the last whorl is composed of 6 relatively large chambers 



