mm. UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



Stratigraphical range. Globigerina belli was described by White (1928) as 

 " being of rare occurrence in the uppermost Mendez, becoming common in the very 

 base of the Velasco, and rapidly diminishing, till disappearing a short distance above 

 the base ". Apparently, White confused the present species with morphologically 

 similar Ritgoglobigerina species from the Upper Maestrichtian, and thus extended its 

 range to the uppermost Mendez. However, in the Esna-Idfu region G. belli occurs 

 as a rare form in the Danian G. compressajG. daubjergensis Zone and in the basal part 

 of the overlying G. angulata Zone of Middle Paleocene age. 



Globigerina chascanona Loeblich & Tappan 

 (PI. 16, figs. 4«-c) 



1957a Globigerina chascanona Loeblich & Tappan : 180— 181, pis. 49, figs, ^a-^c ; pi. 61, 



figs. 8a-c. 

 1960a Globigerina chascanona Loeblich & Tappan ; Berggren : 66-67, pi- J i ^S s - 3 a ~ c '• pi- 7> 



figs. 3a-4c. 



Description. Test medium-sized, coiled in a moderately high trochospire, 

 inflated ; dorsal side slightly raised, with the early whorls moderately elevated above 

 the level of the final whorl ; ventral side quadriglobular, strongly inflated ; equatorial 

 periphery subquadrate to roughly ovoid, lobate ; axial periphery rounded ; chambers 

 on the dorsal side about 12 in number, increasing moderately in size and arranged in 

 2.\ sinistrally coiled whorls ; the initial chambers are small, inflated, globigerine, 

 almost masked by the surface rugosity and are followed by large, roughly ovoid 

 chambers ; the last whorl is composed of 4^, large, slightly ovoid to roughly quadrate 

 chambers ; on the ventral side the chambers are 4J, large, globular, strongly inflated, 

 overlapping and pushed forward towards the much-narrowed umbilicus ; sutures on 

 the dorsal side short, very slightly curved to almost straight, depressed ; on the 

 ventral side they are slightly curved, almost radial and strongly depressed ; umbilicus 

 very narrow, shallow and open, with the last chamber strongly pushed over it ; 

 aperture interiomarginal, umbilical ; surface distinctly nodose, with the nodes taper- 

 ing out especially along the periphery and on the ventral side in the form of thick 

 stout, spine-like projections, giving the surface a very prominently spinose appear- 

 ance. 



Dimensions of described specimen. 



Maximum diameter = 0-38 mm. 



Minimum diameter = 0-32 mm. 



Thickness = 0-28 mm. 



Remarks. This species is distinguished by its small to medium-sized, tightly 

 coiled, medium to relatively highly spired, prominently spinose test ; its narrow 

 umbilicus ; overlapping chambers on the ventral side, and slightly curved depressed 

 sutures. 



Loeblich & Tappan (1957a) showed a wide range of variation in the degree of 

 elevation of the dorsal side of G. chascanona, from a very highly trochospirally 

 coiled test and a high, conical dorsal side in their holotype (pi. 49, figs. 5«-c), to 



