86 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



In the Esna-Idfu region G. area occurs as an abundant form in the G. forncatai 

 Zone and in the lower part of the overlying G. gansseri Zone. It fades out gradually 

 in the upper part of the latter zone, and dies out completely before the overlying 

 G. esnehensis Zone. 



Globotruncana bahijae sp. nov. 



(PI. 6, figs. 2a-d) 



Diagnosis. A Globotruncana with concavo-convex test, weakly developed 

 double keel, wide peripheral band, rough surface and very wide umbilicus. 



Description. Test large, roughly ovoid in outline, concavo-convex, coiled in 

 a very low trochospire ; dorsal side gently concave with the early whorls depressed 

 and the last chambers slightly sloping towards the central part of test, ventral side 

 inflated and moderately protruding ; equatorial periphery roughly ovoid, moderately 

 lobate with two widely spaced, delicately beaded marginal keels which are slightly 

 masked by the surface rugosity ; axial periphery subrounded, subtruncate ; chambers 

 on the dorsal side 15, arranged in 2§ dextrally coiled whorls ; the initial chambers are 

 small, weakly inflated, globigerine, and increase slowly in size ; they are followed by 

 relatively large, subglobular, compressed chambers which increase slightly more 

 rapidly in size ; the last whorl is composed of ^h large, crescentic, compressed 

 chambers which are slightly tilted towards the central part and increase slowly in 

 size ; on the ventral side the chambers are 5-3-, subglobular, slightly elongated in the 

 direction of coiling, strongly inflated, moderately protruding, very loosely coiled and 

 increase slowly in size ; sutures on the dorsal side slightly curved, depressed in the 

 early part, strongly curved, raised and delicately beaded in the last whorl ; on the 

 ventral side the sutures are straight, radial and strongly incised ; umbilicus hexago- 

 nal in outline, very wide, relatively shallow, covered by complex tegilla ; primary 

 apertures interiomarginal, umbilical ; tegilla, with accessory apertures, reasonably 

 well-preserved ; wall calcareous, perforate except for the imperforate keels, peripheral 

 band and tegilla ; surface rough, covered with large papillae which are slightly 

 reduced towards the last chamber ; the two marginal keels are delicately beaded, the 

 dorsal one is alwayswell-developed but the ventral is sometimes almost masked by the 

 surface rugosity ; the two keels slightly diverge from each other and enclose an 

 irregular, relatively wide peripheral band. 



Dimensions of holotype. 



Maximum diameter = 0-45 mm. 



Minimum diameter = 0-32 mm. 



Thickness = 0-20 mm. (of last chamber) 



Main variation 



1. Chambers on the dorsal side 13-18, arranged in 2^-3 whorls, usually dextrally 



coiled, but sinistral forms occasionally occur (of 67 specimens picked at 

 random, 1 coiled sinistrally). 



2. Chambers in the last whorl 5-7 increasing slowly to moderately in size. 



