io 4 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



marginal keels enclosing a wide peripheral band which widens out towards the last 

 chamber ; axial periphery truncate ; chambers on the dorsal side are not all clear but 

 appear to be 15 in number, arranged in 3 dextrally coiled whorls ; initial chambers 

 extremely small, globular, weakly inflated and increase slowly in size ; they are 

 followed by slightly larger, globular inflated chambers which increase slowly in size 

 up to the beginning of the last whorl where they start to enlarge very rapidly ; the 

 last whorl is composed of 4 large, strongly inflated chambers which are roughly 

 globular in the early part, crescentic and strongly elongated in the direction of coiling 

 in the later part and increasing so rapidly in size that the last chamber constitutes 

 about half the test ; on the ventral side the chambers are 4, subglobular in the early 

 part, strongly elongated in the last chamber which constitutes about half of the test ; 

 sutures on the dorsal side curved, raised, beaded, merging into relatively sharp 

 depressions before joining the spiral suture ; on the ventral side the sutures are 

 radial and depressed ; umbilicus irregular in outline, relatively wide, deep, bordered 

 by weakly raised, delicately beaded umbilical ridges, and covered by complex tegilla 

 of which remnants are still preserved ; primary apertures interiomarginal umbilical ; 

 tegilla, with accessory apertures, only poorly preserved ; wall calcareous, perforate 

 except for the imperforate keels, peripheral band and tegilla ; surface rough, 

 delicately papillose, with the roughness decreasing gradually towards the last 

 chamber. 



Dimensions of described specimen. 



Maximum diameter = 0-43 mm. 



Minimum diameter = 0-31 mm. 



Thickness = 0-25 mm. 



Variation. The main variation observed in this subspecies is in the degree of 

 inflation of the chambers in the last whorl, the degree of surface plication on the 

 dorsal side and in the surface roughness. 



Remarks. Globotruncana fomicata cesarensis was first described by Gandolfi 

 (1955) and considered to represent a final stage in the evolution of the G. fornicata 

 group, characterized by the reduction in the size of test and in the number of chamb- 

 ers in the last whorl. The present study substantiates Gandolfi's conclusion, although 

 his G. fornicata plummevae which he regarded as the ancestor of G. fornicata cesar- 

 ensis, is here considered a junior synonym of G. fornicata fornicata Plummer. 



Specimens of G. fornicata cesarensis, from the Esna-Idfu region, conform well with 

 Gandolfi's original description and figures. However, two distinct morphological 

 types of this subspecies were recorded, one with a smooth test and a non-inflated 

 dorsal side (e.g. PI. 13, figs. 30-c), the other with a moderately to distinctly inflated 

 dorsal side and a rougher surface. The former type was clearly observed high in the 

 section while the latter was found to flood the lower part. It is possible that further 

 study may prove these types to be worthy of distinction. However, as such varia- 

 tion was mentioned by Gandolfi (1955), and as the former type was found to be rather 

 rare in the samples studied, the two forms are here assigned to the same subspecies. 



Hypotypes. P.45530. 



