IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 233 



leading to G. pusilla laevigata Bolli, by the slight flattening of the dorsal side, the 

 development of an acute axial periphery and a partially or completely developed keel ; 

 the other to G. pusilla mediterranica subsp. nov. by the increase in the size of test, 

 greater protrusion of the ventral side, the development of quadrangular chambers on 

 the dorsal side, the pseudo-keel and the surface rougosity. Moreover, G. convexa 

 Subbotina might possibly have evolved from G. pusilla pusilla by reduction in the 

 size of test, development of surface spines and the bulla-like last chamber. 



Hypotype. P. 45626. 



Horizon and locality. Figured specimen, from sample No. 37, Gebel Owaina 

 section. 



Stratigraphical range. Globorotalia pusilla pusilla was first described by 

 Bolli (19576) from the Paleocene lower Lizard Springs formation of Trinidad, where 

 it characterizes the G. pusilla pusilla Zone, and continues through the lower part of 

 the overlying G. pseudomenardii Zone. It is also recorded from the so-called Lower 

 Montian of northern Italy (Bolli & Cita 1960a, b) and Montian of Austria (Hillebrandt 

 1962). 



In the Esna-Idfu region, G. pusilla pusilla appears in the uppermost part of the 

 G. uncinata Subzone, and continues in the basal part of the G. pseudomenardii 

 Subzone where it dies out completely. Between the limits of these two subzones it 

 floods the succession, thus characterizing the G. pusilla Subzone, of upper Middle 

 Paleocene age. 



Globorotalia quadrata (White) 

 (PI. 18, figs. 4«-c) 



1928a Globigerina quadrata White : 195, pi. 27, figs. 18a, b. 



19576 Globorotalia quadrata (White) Bolli : 73-74, pi- 17, figs. 22-24. 



J 959 Globigerina quadrata White ; Nakkady (pars) : 461, pi. 3, figs. ^a-c. 



Description. Test medium-sized, inflated, coiled in a very low trochospire ; 

 dorsal side depressed in the early part, inflated later ; ventral side more strongly 

 inflated ; equatorial periphery quadrate and distinctly lobate ; axial periphery 

 rounded ; chambers, 12, arranged in 2\ dextrally coiled whorls ; the initial ones are 

 small, slightly inflated ; the last whorl is composed of 4! large, globular, inflated 

 chambers which increase rapidly in size except for the last which is slightly smaller 

 than the penultimate and is slightly compressed ; on the ventral side the chambers 

 are 4J, large, globular and strongly inflated ; sutures on the dorsal side curved, 

 depressed in the early part, almost straight, radial and depressed later ; on the 

 ventral side the sutures are radial and strongly depressed ; umbilicus irregular in 

 outline, relatively wide, deep and open ; aperture a narrow crescentic arch, interio- 

 marginal, extraumbilical-umbilical ; wall calcareous, perforate ; surface of early 

 chambers finely cancellate, becoming smoother towards the last chamber. 



Dimensions of described specimen. 

 Maximum diameter = 0-43 mm. 

 Minimum diameter = 0-26 mm. 



Thickness = 0-25 mm. 



