IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 107 



named G. fornicata globulocamerata ; it is distinguished by a tendency to have 

 globular chambers in the last whorl instead of the extremely elongated chambers of 

 the central type. 



The lumping of these subspecies and their transitional forms as G. fornicata 

 Plummer has confused the diagnostic features and stratigraphical range of G. 

 fornicata fornicata. However, it is clearly distinguished by its biconvex test, 

 extremely elongated chambers in the last whorl which are slightly plicate on the 

 dorsal side and sometimes inflated towards their inner extremities, and strongly 

 overlapping on the ventral side ; its curved, raised, beaded, ventral sutures and 

 strongly diverging double keel. 



Glaessner (1937 : 43, text-fig. 5) suggested the evolution of G. fornicata Plummer 

 from Rotalipora appenninica (Renz), in Coniacian-Santonian time through a yet 

 unknown form. However, Bolli (1951) and Gandolfi (1955, pi. 10) suggested its 

 evolution from G. lapparenti lapparenti (Brotzen) while Bronnimann & Brown (1956) 

 suggested that it evolved from G. imbricata Mornod. Moreover, Gandolfi (1955) 

 suggested the evolution of G. fornicata fornicata Plummer from G. fornicata manaur- 

 ensis by the gradual reduction of the tight coiling of the chambers, by the reduction 

 in the number and degree of overlap of chambers, and by the anterior divergence of 

 the two keels. It is also evident that members of the G. fornicata group have 

 gradually evolved into the corresponding members of the G. contusa group, through 

 various transitional stages, as was partly mentioned by Glaessner (1937), Bolli (1951), 

 Gandolfi (1955), and Bronnimann & Brown (1956), and is clearly documented in the 

 present study. 



G. fornicata fornicata is believed to have evolved into G. contusa contusa through 

 G. contusa witwickae subsp. nov., and into G. contusa sensu Troelsen through G. 

 fornicata globulocamerata subsp. nov. 



Hypotypes. P. 45531. 



Horizon and locality. Figured specimens, PI. 13, figs. 5«-c, from sample No. 

 14, G. A 314 ; fig. 6, from sample No. 3, Abou Saboun section ; PI. 14, figs, la-c from 

 sample No. 4 Abou Saboun section. 



Stratigraphical range. Globotruncana fornicata fornicata Plummer was first 

 described from the Upper Taylor (Campanian) Formation of Texas (Plummer 1931, 

 sta. 226-T-8) and was recorded as very common to abundant in Taylor and Navarro 

 strata which, according to Bolli (1957, 1959), corresponds to the Upper Santonian- 

 Lower Maestrichtian of Western Europe. It was recorded from the same horizon 

 by Cushman & Todd (1943), Cushman (1944, 1946, 1948), and by Frizzell (1954) who 

 showed that it ranges throughout the whole Taylor and Lower Navarro groups, 

 being most abundant in the upper Taylor beds, and that it never occurs below the 

 base of the Taylor formation. Albritton & Phleger (1937) restricted its range to the 

 Taylor group only, while Bronnimann & Brown (1956) recorded its range as Coniacian 

 to Campanian, possibly Maestrichtian. Hagn (1953) described it from the Upper 

 Campanian of Germany, Barr (1962) from the Campanian of the Isle of Wight, 



