IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 113 



sition which is substantiated by the occurrence of several transitional stages (see 

 PI. 2, figs. ^a-d). 



On the other hand, forms which can be morphologically considered as transitional 

 between G. gagnebini and G. aegyptiaca aegyptiaca were recorded, and may suggest 

 the evolution of the former into the latter. But the fact that the two species have 

 always been confused with each other does not allow one to distinguish precisely 

 their respective stratigraphical ranges which are generally considered to be the same. 

 However, the apparent morphological similarity of the two species may be due to 

 " parallel evolution " from two distinct but genetically related forms. 



Hypotypes. P. 45538. 



Horizon and locality. Figured specimens, P1.2, figs. la-d, 2a-d ; PI. 3, 

 fig. 6, from sample No. 16, W. El-Sharawna section ; PL 2, figs, ^a-d, which is a 

 transitional stage to G. ventricosa White, and PL 3, figs, ^a-d, from sample No. 18, 

 W. El-Sharawna section ; PL 2, figs. <\a-d, from sample No. 4, Abou Saboun section ; 

 PL 3, figs. la-d, from sample No. 11, Gebel Owaina section. 



Stratigraphical range. Globotruncana gagnebini was first described by Tilev 

 (1951) from the Maestrichtian of southeastern Turkey where it was recorded to 

 range throughout the stage. It was also recorded from the Maestrichtian of Trinidad 

 (Bolli 1951, 1957a) as ranging throughout the G. gansseri and the Abathomphalus 

 mayaroensis Zones. 



In the Esna-Idfu region, G. gagnebini Tilev floods the Maestrichtian part of the 

 studied sections ; it is abundant in the G. fornicata Zone, floods the G. gansseri Zone 

 and is rare in the G. esnehensis Zone, where it dies out completely. 



Globotruncana cf. gagnebini Tilev 



(PL 3, figs. 2a-d) 



Remarks. The tendency of G. gagnebini Tilev to have a slightly raised dorsal 

 side was mentioned by Tilev (1951) and was observed in the present study. How- 

 ever, none of Tilev's figures nor the typical specimens here studied, was found to have 

 a conical dorsal side. The form here described as G. cf. gagnebini is closely related to 

 Tilev's form, but differs only in having a gently coned, dorsal side. Morphologically, 

 this form should be considered separately, but because it was found to be rather 

 rare in the samples studied, it is provisionally described as G. cf. gagnebini. 



Hypotype. P.45539. 



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

 section. 



Stratigraphical range. Globotruncana cf. gagnebini is rare in the Lower 

 Maestrichtian G. fornicata Zone and in the basal part of the Middle Maestrichtian 

 G. gansseri Zone of the Esna-Idfu region. 



