IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 97 



probably belongs to the present subspecies, was recorded from the Upper Campanian 

 of central Poland. Records of G. contusa contusa (Cushman) from rocks older than 

 the Middle Maestrichtian may be of G. contusa witwickae. 



Globotruncana cf. convexa Sandidge 

 (PL i, figs, sa-c) 



1932 Globotruncana convexa Sandidge : 285, pi. 44, figs. 9-1 1. 



Description. Test small, biconvex, coiled in a low trochosphire ; dorsal side, 

 moderately arched, ventral side weakly inflated and slightly protruding ; equatorial 

 periphery roughly ovoid or rather quadrate, distinctly lobate, with two well-develop- 

 ed, heavily beaded keels enclosing a wide, inclined peripheral band ; axial periphery 

 truncate ; chambers on dorsal side 15, arranged in 3 dextrally coiled whorls ; the 

 initial chambers are very small, globigerine, inflated and increase slowly in size ; 

 the last whorl is composed of 4 large, crescentic chambers which are distinctly 

 flattened, elongated in the direction of coiling and increase moderately in size ; on the 

 ventral side the chambers are 4, large, ovoid, weakly inflated and slightly overlapping ; 

 sutures on the dorsal side curved, raised and heavily beaded ; on the ventral side the 

 sutures are strongly curved forward, slightly raised and beaded ; umbilicus roughly 

 quadrangular in outline, wide, deep, bordered by raised, beaded ridges and covered 

 by complex tegilla of which remnants are still preserved ; primary apertures interio- 

 marginal, umbilical ; tegilla with accessory apertures only poorly preserved ; 

 wall calcareous, perforate except for the imperforate keels, peripheral band and 

 tegilla ; surface delicately papillose in the early part, becoming smoother towards 

 the last chamber. 



Dimensions of described specimen. 

 Maximum diameter = 0-40 mm. 

 Minimum diameter = 0-30 mm. 



Thickness = 0-17 mm. 



Remarks. Cushman & Hedberg (1941) followed by Cushman & Deaderick (1944), 

 Cushman (1946), Cita (1948), Hagn (1953) and Graham & Clark (1961) considered 

 G. convexa Sandidge to be a junior synonym of G. fornicata Plummer. However, as 

 can be seen from the original description and figures of Sandidge (1932) and from the 

 samples here studied, G. convexa is more closely related to G. area (Cushman) than 

 to G. fornicata Plummer and should be considered separately. 



The specimens here described as G. cf. convexa Sandidge differ from the holotype 

 in being less convex on the dorsal side and in having slightly raised ventral sutures. 

 Sandidge described the ventral keel on the holotype as poorly developed, while on 

 the specimen here figured the two keels are both well-developed, although the 

 tendency towards a less developed ventral keel was clearly observed. 



Globotruncana convexa is believed to have evolved from G. area (Cushman) by a 

 reduction in size of test and in the number of chambers, and by the development of 

 surface rugosity. 



Hypotype. P.45526. 



