IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 103 



side the chambers are 4, large, subglobular in the early part, ovoid in the last chamber, 

 strongly inflated and increase rapidly in size ; sutures on the dorsal side curved, 

 raised, delicately beaded and merge into relatively shallow depressions from the 

 periphery inwards towards the spiral suture ; on the ventral side the sutures are 

 radial and depressed ; umbilicus irregular in outline, wide, deep and covered by 

 complex tegilla of which remnants are still preserved ; primary apertures interio- 

 marginal, umbilical ; tegilla, with accessory apertures, only poorly preserved ; 

 wall calcareous, perforate except for the imperforate keels, peripheral band and 

 tegilla ; surface rough, coarsely papillose. 



Dimensions of described specimen. 

 Maximum diameter = 0-38 mm. 



Minimum diameter = 0-29 mm. 



Thickness = 0-22 mm. 



Variation. The main variation observed in G. fornicata ackermanni is in the 

 degree of inflation of both sides, imbricate arrangement of keels, rate of growth and 

 surface rugosity. 



Remarks. Globotruncaca fornicata ackermanni is believed to have evolved from 

 G. fornicata fornicata Plummer by reduction in the size of test, greater inflation of 

 the chambers, imbricate arrangement of keels and peripheral band and the develop- 

 ment of surface rugosity. The form here figured (PL 14, figs, ^a-d) shows inter- 

 mediate characters between the two subspecies and is thus considered as a transition- 

 al stage. 



Hypotypes. P.45529. 



Horizon and locality. Figured specimes, from sample No. 4, Abou Saboun 

 section. 



Stratigraphical range : Gandolfi (1955) described G. fornicata ackermanni 

 from the Colon shale of northeastern Colombia, where he considered its range as 

 Campanian-Lower Maestrichtian. It was also recorded from the Maestrichtian of 

 Um El-Huetat section west of Safaga, Eastern Desert, Egypt (Ansary & Fakhr, 1958). 



In the Esna-Idfu region, G. fornicata ackermanni occurs as a common to abundant 

 form in the Lower Maestrichtian G. fornicata Zone and dies out completely towards 

 the top part of this zone. 



Globotruncana fornicata cesarensis Gandolfi 



(PL 13, figs. 3«~4c ; PL 14, figs. 6a-c) 



1955 Globotruncana fornicata cesarensis Gandolfi : 45, pi. 2, figs. loa-c. 



Description. (Specimen, PL 14, figs. 6a-c.) Test medium-sized, biconvex, 

 coiled in a low trochospire ; dorsal side convex, moderately inflated, and slightly 

 folded in the last chamber, ventral side slightly inflated ; equatorial periphery 

 roughly ovoid, moderately lobate, with two well-developed, delicately beaded 



