156 I lU'ER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



interiomarginal, umbilical position and by the loss of the umbilical portici, or from 

 the rounded Globorotalia by the confinement of the aperture to an interiomarginal, 

 umbilical position, is still unknown. Nevertheless the recorded development of 

 Globigerina triloculinoides Plummer from Globorotalia pseudobulloides (Plummer) (see 

 Hofker ig6og, i ; Berggren 1962) may favour the last-mentioned proposition. 



The present study of early representatives of the genus Globigerina throughout the 

 Paleocene-Lower Eocene succession of the Esna-Idfu region has shown that the 

 genus displays a marked tendency to increase its surface rugosity upwards in the 

 section (see Text-fig. 13) 



Globigerina alanwoodi sp. nov. 

 (PI. 16, figs. 6a-c) 



Diagnosis. A Globigerina with large, robust, smooth-walled, multilocular test ; 

 weakly raised dorsal side and strongly inflated ventral one ; numerous, inflated 

 chambers which increase slowly in size ; wide umbilicus. 



Description. Test large, robust, coiled in a low trochospire ; dorsal side almost 

 flat, slightly inflated, with the early chambers very weakly raised over the circumam- 

 bient last whorl ; ventral side strongly inflated and distinctly protruding ; equatorial 

 periphery circular, slightly lobate ; axial periphery rounded ; chambers on the dorsal 

 side 17, arranged in 3 dextrally coiled whorls ; the initial chambers are comparatively 

 large, globular, slightly inflated and are followed by roughly ovoid, moderately 

 inflated ones which are elongated in the direction of coiling and increase regularly in 

 size ; the last whorl is composed of 7 large chambers which are crescentic in the early 

 part, roughly quadrangular later, strongly elongated in the direction of coiling and 

 increase slowly and regularly in size, except for the last chamber which is slightly 

 smaller than the penultimate ; on the ventral side the chambers are 7, large, inflated 

 and strongly protruding ; sutures on the dorsal side slightly curved, depressed ; on 

 the ventral side they are straight, radial and strongly incised ; umbilicus wide, deep 

 and open, aperture interiomarginal, umbilical ; wall calcareous, perforate ; surface 

 smooth, except around the umbilicus where it becomes delicately papillose. 



Dimensions of holotype. 



Maximum diameter = 0-47 mm. 



Minimum diameter = 0-41 mm. 



Thickness = 0-30 mm. 



Remarks. Globigerina alanwoodi sp. nov. is closely related to G. mckannai 

 White from which it is distinguished by its perfectly smooth surface, and distinct 

 stratigraphical range. It probably evolved into G. mckannai in Upper Paleocene 

 time by the development of the granular spinose surface. On the other hand, it 

 possibly evolved from the smooth surfaced, multilocular, G. spiralis Bolli, by flatten- 

 ing the dorsal side, increasing the size of test and the number of chambers in the last 

 whorl and by developing a much wider umbilicus. The stratigraphical ranges of 

 these forms agree with this proposition, although no direct evidence was recorded. 



