IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 85 



interpreted Cushman's single-keeled form as G. rosetta (Carsey), while Bolli (1951) 

 stated that it probably belongs to the Globotruncana stuarti group. Gandolfi (1955) 

 made this form the basis of a new species which he named Globotruncana bollii, 

 while Dalbiez (1955) considered it to belong to his subspecies G. elevata stuartiformis 

 Dalbiez, [=G. stuarti stuartiformis Dalbiez]. 



Gandolfi (1955) described Globotruncana area caribica as a new subspecies of 

 G. area (Cushman) and thus changed the latter's name to G. area area (Cushman) . 

 However, G. area caribica appears to be a junior synonym of G. gagnebini Tilev 1951, 

 thus the name G. area (Cushman) is here retained. Similarly, Said & Kerdany (1961) 

 described as G. area (Cushman) from the Maestrichtian chalk of the Farafra Oasis, 

 Egypt, a form which probably belongs to G. gagnebini Tilev. 



Globotruncana area (Cushman) is believed to have evolved from the G. linneiana 

 (d'Orbigny) (=G. lapparenti Brotzen) stock as previously mentioned by Cita (1948), 

 Bolli (1951), Bronnimann & Brown (1956) and Berggren (1962). On the other hand, 

 G. area was itself found to show three main evolutionary tendencies which are as 

 follows : 



1. A tendency towards the reduction of the ventral keel on the final chambers 



leading to G. leupoldi Bolli. 



2. A tendency towards the flattening of the ventral side and the reduction of the 



ventral keel leading to G. orientalis sp. no v. 



3. A tendency to reduce the size of test and the number of chambers in the last 



whorl leading to G. convexa Sandidge. (see PI. 1, figs. 3a-c.) 

 The morphological characters and stratigraphical ranges of the five species 

 (G. linneiana, G. arca,G. leupoldi, G. orientalis and G. convexa) support this hypothesis. 



Hypotypes. P.45517. 



Horizon and locality. Figured specimens PI. 1 figs. la-c, 2, from sample No. 4, 

 Abou Saboun section, and figs. 3«-c, from sample No. 23, W. El-Sharawna section. 



Stratigraphical range : The species was first described from the upper part 

 of the Papagallos shales (Mendez shale) of Mexico which was later considered to be of 

 Maestrichtian age. 



Analysis of all previous records of G. area (Cushman) shows that it has a world-wide 

 distribution, and that it occurs mainly in the Maestrichtian and the uppermost 

 Campanian. However, owing to misidentification of the species and confusion with 

 various other species, its true stratigraphical range has hitherto been obscured. 

 Bronnimann & Brown (1956) stated that G. area appears to be restricted to Maestrich- 

 tian strata and that all occurrences reported from pre-Maestrichtian strata are 

 probably erroneous. They added that it is best developed in Upper Maestrichtian 

 strata, and this was partially substantiated by Berggren (1962 : 51). However, 

 G. area was recorded by Barr (1962) from the uppermost part of the Belemnitella 

 mucronata Zone of the Isle of Wight, England, and from the Upper Campanian of the 

 Paris Basin by the present author. 



