IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 81 



truncana aegyptiaca duwi is believed to have evolved from G. aegyptiaca aegyptiaca as 

 suggested by their morphological features and stratigraphical distribution. 



Gandolfi (1955 : 21, 22 ; text-fig. 5, 2a-c) included in his G. tricar inata colombiana, 

 a form which possibly belongs to G. aegyptiaca duwi. 



Hypotype. P.45514. 



Horizon and locality. Figured specimen from sample No. 16, Gebel Owaina 

 section. 



Stratigraphical range. Nakkady (1950) described G. aegyptiaca duwi from 

 the Upper Cretaceous chalk of Gebel. Duwi section, Kossier area, Eastern Desert, 

 Egypt, where it was described as rather frequent. It was also recorded from the 

 Campanian-Maestrichtian of southern and western Sinai, Egypt (Nakkady & Osman 

 1954) and from the Maestrichtian of Um El-Huetat section, Eastern Desert, Egypt 

 (Ansary & Fakhr 1958). 



In the Esna-Idfu region, G. aegyptiaca dtiwi appears in the basal part of the 

 G. gansseri Zone, and increases gradually in number upwards in the section becoming 

 abundant in the upper part of this zone, and then fades out gradually, dying out 

 completely at the top of the overlying G. esnehensis Zone. 



Globotruncana arabica sp. nov. 



(PL 6, figs. 3a-d ; PI. 11, fig. 4) 

 Diagnosis. A Globotruncana with large, concavo-convex, strongly umbilico- 

 convex test ; entirely single keel strongly shifted towards dorsal side ; chambers 

 increasing slowly in size and distinctly inflated on ventral side ; very rough surface 

 and large umbilicus. 



Description. Test large, subcircular, globular in outline, concavo-convex, 

 distinctly umbilico-convex, coiled in a very low trochospire ; dorsal side shallowly 

 concave, flat in the early part, slightly tilted inward in the last whorl ; ventral side 

 strongly inflated and distinctly protruding ; equatorial periphery subcircular, 

 globular and distinctly lobate, with a single, well developed, beaded keel which is 

 strongly shifted towards the dorsal side ; axial periphery subrounded, very gently 

 truncate ; chambers on the dorsal side about 17, arranged in 3 dextrally coiled 

 whorls ; the initial chambers are small, globular, weakly inflated, almost masked by 

 the surface rugosity and are followed by slightly larger, subglobular, weakly inflated 

 ones ; the last whorl is composed of 5 large, subglobular, compressed chambers 

 which increase slowly in size, are slightly elongated in the direction of coiling and 

 strongly tilted inward towards the initial part ; on the ventral side the chambers are 

 5, large, subglobular, strongly inflated, distinctly protruding, and enlarging so slowly 

 that they all appear roughly equal in size ; sutures on the dorsal side are slightly 

 curved, depressed in the early part, very short, slightly curved to almost straight in 

 the later part, raised and beaded on the periphery, becoming depressed inward ; on 

 the ventral side the sutures are straight, radial, and strongly depressed ; owing to the 



