i 4 -f UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



characters is well known in populations of G. ventricosa White and is not considered 

 of any taxonomic importance. Thus G. ventricosa carinata Dalbiez is considered a 

 junior synonym of G. ventricosa White. Similarly, the holotype of G. ventricosa 

 primitiva Dalbiez, although not well preserved, is identical with G. concavata (Brot- 

 zen) of which it is here considered a junior synonym. 



Globotruncana ventricosa White was also confused with G. gagnebini Tilev (e.g. 

 Bolli 1951, Gandolfi 1955, etc.) and with G. tricarinata (Quereau) (e.g. Mornod 1950). 

 It has possibly evolved from G. tricarinata tricarinata (Quereau) and into G. gagnebini 

 Tilev, although Gandolfi (1955) suggested its evolution from G. tricarinata colombiana. 



Hypotype. P.45563. 



Horizon and locality. Hypotype from sample No. 16, W. El-Shasawna 

 section. 



Stratigraphical range. White (1928) described this species from the Campan- 

 ian, Papagallos shale of Mexico, and Bolli (1957a) restricted its range to his Globo- 

 truncana stuarti Zone which he considered as Upper Campanian. It was also 

 recorded from the Campanian-Maestrichtian of southwestern Sinai, Egypt (Nakkady 

 & Osman 1952) and from the Upper Santonian of Tunisia (Dalbiez 1955). 



In the Esna-Idfu region, G. ventricosa is rare in the Lower Maestrichtian G. 

 fornicata Zone and in the lower part of the Middle Maestrichtian G. gansseri Zone, 

 where a great number of transitional stages occur between it and G. gagnebini 

 (e.g. PI. 2, figs. ^a-d). 



Globotruncana youssefi sp. nov. 



(PI. 6, figs. 4a-d) 



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

 test ; distinctly lobate periphery; entire single keel ; globigerine early part and crescen- 

 tic later chambers ; strongly curved, raised beaded dorsal sutures ; peculiarly shaped 

 last chamber slightly tilted towards the umbilicus, surface rough. 



Description. Test large, planoconvex, umbilico-convex, coiled in a low trocho- 

 spire ; dorsal side almost flat and weakly imbricate, with the last chambers slightly 

 lower than the early ones; ventral side strongly inflated and very distinctly pro- 

 truding ; equatorial periphery subcircular, distinctly lobate with a single, well- 

 developed, much thickened and beaded marginal keel ; axial periphery subangular ; 

 chambers on the dorsal side 19, arranged in 3 dextrally coiled whorls ; the initial 

 chambers are very small, globular and inflated ; they increase slowly in size, and are 

 followed by relatively larger, globular, weakly inflated chambers which tend to be 

 slightly elongated in the direction of coiling ; the last whorl is composed of 5| large, 

 crescentic chambers which increase slowly in size, except for the last which has a 

 peculiar angular shape that makes it appear slightly smaller than the penultimate ; 

 on the ventral side the chambers are 5|, large, angular conical, strongly inflated and 

 distinctly protruding ; sutures on the dorsal side short, radial, depressed in the early 

 part, distinctly curved, raised and beaded in the later part, although the beading 



