IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 117 



Globotruncana gansseri gansseri Bolli 



(PL 5, figs. la-d; PL n, fig. 3) 



1951 Globotruncana gansseri Bolli : 196, 197 ; pi. 35, figs. 1-3. 



1956 Rugotruncana gansseri (Bolli) Bronnimann & Brown : 549-550 ; pi. 23, figs. 7—9 ; 

 text-fig. 23. 

 ? i960 Globotruncana monmouthensis Olsson : 50-51, pi. 10, figs. 22-24. 

 ? i960 Globotruncana (Rugotruncata) gansseri, Bolli; Pessagno : 102, pi. 4, fig. 11. 



Emended diagnosis. A Globotruncana with large, planoconvex, umbilico- 

 convex test, large chambers increasing very rapidly in size in last whorl ; chambers 

 typically crescentic and strongly elongated in direction of coiling on dorsal side, and 

 angular conical, distinctly protruding on ventral side ; entirely single keel in last 

 whorl, curved, raised, beaded dorsal sutures and slightly curved, depressed ventral 

 ones ; very large umbilicus and moderately to heavily papillose surface in early part 

 of test. 



Description. Test large, planoconvex, umbilico-convex, coiled in a very low 

 trochospire ; dorsal side flat, ventral side strongly inflated and distinctly protruding ; 

 equatorial periphery roughly ovoid, moderately lobate, with a single well-developed, 

 beaded keel ; axial periphery truncate, angular acute ; chambers on the dorsal side 

 15, arranged in 2 J, dextrally coiled whorls ; the initial chambers are small, globular, 

 compressed ; they increase slowly in size and are followed by typically crescentic, 

 much flattened chambers which increase rapidly in size ; the last whorl is composed 

 of 5 large, crescentic, flattened chambers which are elongated in the direction of 

 coiling and increase rapidly in size ; on the ventral side the chambers are 5, large, 

 angular conical, strongly inflated and distinctly protruding ; sutures on the dorsal 

 side curved, raised and beaded ; on the ventral side the sutures are very slightly 

 curved to almost straight, radial and depressed ; umbilicus roughly pentagonal in 

 outline, very wide, deep, bordered by raised, beaded 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 keel and tegilla ; surface smooth on the dorsal 

 side, coarsely papillose on the ventral, with the papillae becoming coarse and scattered 

 towards the last chamber. 



Dimensions of described specimen. 

 Maximum diameter = 0-62 mm. 

 Minimum diameter = 0-47 mm. 



Thickness = 0-30 mm. 



Main variation. 



1. Chambers 14-16, arranged in 2J-3 whorls, generally dextrally coiled (all 



studied specimens coiled dextrally). 



2. Chambers in the last whorl 4^-5. 



Remarks. Globotruncana gansseri was first validly described by Bolli (1951) 

 although he had previously (1950) used the name without giving any description or 



