8o ll'PER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



In the Esna-Idfu region, G. aegyptiaca aegyptiaca floods the whole of the Maestrich- 

 tian section, being extremely abundant in the G. fornicala and G. gansseri Zones, 

 fading out gradually in the top part of the overlying G. esnehensis Zone, and dying 

 out completely just below the disconformity separating the Maestrichtian from the 

 overlying Paleocene. 



Globotruncana aegyptiaca duwi Nakkady 



(PL 3, figs. $a-c) 



1950 Globotruncana aegyptiaca Nakkady var. duwi Nakkady : 690, pi. 90, figs. 17-19. 



1954 Globotruncana aegyptiaca var. duwi Nakkady : Nakkady & Osman : 76, pi. 20, figs. 2ia-c. 



Emended diagnosis : A Globotruncana aegyptiaca with much smaller test 

 and fewer chambers increasing very rapidly in size in last whorl ; ovoid to subtriangu- 

 lar, slightly lobate periphery, and rougher surface. 



Description. Test medium-sized, roughly ovoid in outline, planoconvex, 

 umbilicoconvex, coiled in a very low trochospire ; dorsal side almost flat, ventral side 

 distinctly protruding ; equatorial periphery roughly ovoid, moderately lobate, 

 with two well-developed, beaded keels ; axial periphery truncate ; chambers on 

 the dorsal side, 11, arranged in 2 dextrally coiled whorls ; the initial chambers are 

 small, globigerine, inflated, almost masked by the surface rugosity and increase 

 slowly in size ; the last whorl is composed of 4 chambers which increase so rapidly 

 in size that the last one constitutes about half of the test ; on the ventral side the 

 chambers are 4, large, strongly inflated, distinctly protruding and increase very 

 rapidly in size ; sutures on the dorsal side are curved, raised and beaded ; on the 

 ventral side they are slightly curved forward, depressed and beaded ; umbilicus 

 roughly quadrate in outline, relatively wide, deep, bordered by thick, raised, beaded 

 ridges and covered by complex tegilla of which remnants are still preserved ; 

 primary apertures interiomarginal, umbilical ; tegilla with accessory apertures only 

 poorly preserved ; wall calcareous, perforate except for the imperforate keels, 

 peripheral band and tegilla ; surface rough, distinctly papillose and spinose in the 

 early part, with the roughness decreasing gradually towards the last chamber ; the 

 two marginal keels are almost parallel to each other and enclose a wide, depressed, 

 slightly inclined peripheral band. 



Dimensions of described specimen. 



Maximum diameter = 0-40 mm. 



Minimum diameter = 0-30 mm. 



Thickness = 0-22 mm. 



Remarks. Globotruncana aegyptiaca duwi was first described by Nakkady (1950) 

 as a variety of G. aegyptiaca. However, the present study has shown that it is 

 morphologically distinct from G. aegyptiaca aegyptiaca and that it appears in strati- 

 graphically younger strata. Thus it is here raised to subspecific rank, although 

 Berggren (1962) stated that it can probably be included in G. aegyptiaca s.s. Globo- 



