IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 75 



Globotruncana adamsi sp. nov. 



(PL 8, figs. 2a-d.) 



Diagnosis. A Globotruncana distinguished by its small to medium-sized, dome- 

 shaped, distinctly spiroconvex test ; its highly convex dorsal side and almost flat 

 ventral one .; globigerine, strongly inflated early chambers and crescentic, distinctly 

 elongated, gently plicate ones in the last whorl ; ovoid, slightly to moderately over- 

 lapping chambers on ventral side ; two well-developed marginal keels, wide inclined 

 peripheral band, and generally smooth to delicately papillose surface. 



Description. Test large, spiroconvex, roughly ovoid in outline ; dorsal side 

 highly convex and moderately inflated ; ventral side almost flat ; equatorial peri- 

 phery ovoid, slightly lobate, with two well-developed, heavily beaded marginal 

 keels ; axial periphery truncate, bluntly subangular ; chambers on the dorsal side 

 not all clear, but apparently 23 in number, arranged in 4 dextrally coiled whorls ; 

 the initial chambers are small, globular, weakly inflated and increase very slowly in 

 size ; they are followed by slightly larger, strongly inflated, globular chambers 

 which increase moderately in size ; the last whorl is composed of 5 large chambers 

 which increase rapidly in size, and are subglobular and strongly inflated in the early 

 part, becoming crescentic, strongly elongated in the direction of coiling later ; the 

 last chamber is weakly plicated ; on the ventral side there are 5 chambers which 

 increase moderately in size, being subglobular in the early part, ovoid, slightly 

 inflated and strongly overlapping later ; sutures on the dorsal side slightly curved, 

 depressed in the early part, strongly curved, raised and distinctly beaded later ; on 

 the ventral side the sutures are straight, radial, strongly depressed at first, curved 

 forward, delicately beaded, slightly raised or running in sutural depressions later ; 

 umbilicus roughly pentagonal in outline, wide, deep, bordered by slightly raised, 

 delicately beaded umbilical ridges, and covered by complex tegilla of which rem- 

 nants 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 delicately papillose 

 especially on the ventral side ; the two marginal keels are well-developed and heavily 

 beaded, the ventral one is slightly shifted towards the ventral side, and thus they 

 enclose a relatively wide, slightly inclined peripheral band which becomes progres- 

 sively narrower towards the last chamber. 



Dimensions of holotype. 



Maximum diameter = 0-46 mm. 



Minimum diameter = 0-36 mm. 



Thickness = 0-25 mm. (Across middle part of test) 



Main variation. 



1. Chambers 13-24, arranged in 3-4 whorls, generally dextrally coiled. 



2. Chambers in the last whorl 4-6. 



3. The two keels are either equally developed or the ventral one slightly weakens 



towards the last chamber. 



