IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 99 



preserved ; primary apertures interiomarginal, umbilical ; tegilla with accessory 

 apertures only poorly preserved ; wall calcareous, perforate except for the imperfo- 

 rate keel and tegilla ; surface delicately papillose especially on the early part and on 

 the ventral side. 



Dimensions of described specimen. 

 Maximum diameter = 0-50 mm. 



Minimum diameter = 0-44 mm. 



Thickness = 0-27 mm. 



Main variation. 



1. Chambers 15-21, arranged in 3-4 whorls usually dextrally coiled, but sinistral 



forms also occur (out of 500 specimens selected at random, 28 coiled sinis- 

 trally). 



2. The last whorl is composed of 5-7 chambers, normally 6, varying in shape from 



typically petaloid to slightly elongate or even roughly rectangular, and in 

 the degree of inflation on the ventral side which may give it a weakly or 

 distinctly undulating appearance. 



Remarks. Globotruncana ensehensis was first described by Nakkady (1950) as 

 a variety of Globotruncana area (Cushman). Nakkady & Osman (1954) realizing the 

 great difference between this form and G. area (Cushman), quite justifiably raised it 

 to specific rank. Hofker (1956c: 75) and Berggren (1962 : 31) considered G. esnehen- 

 sis as a junior synonym of Abathomphalus intermedia (Bolli), but the two species are 

 too remote to be related to each other. Again, Said & Kenawy (1956) described as 

 G. intermedia Bolli, and G. caliciformis Vogler, forms which are actually G. esnehensis. 



The evolutionary history of G. esnehensis is not clearly known because its strati- 

 graphical range has been somewhat confused. However, its morphological similarity 

 to both G. orientalis sp. nov. and G. fareedi sp. nov., which appear earlier in the 

 section, may suggest its evolution from one of these species, although no direct 

 evidence was recorded. Again, it is possible that G. esnehensis has evolved from 

 G. conica White, although the morphological characters and stratigraphical range of 

 the latter species have been very much confused. 



Specimens of G. esnehensis, from the Esna-Idfu region, conform well with the 

 holotype of G. area (Cushman) var. esnehensis of Nakkady (1950) (B.M.N.H., 

 P. 41780), the paratypes (P.41781), and with the description and figures of Nakkady 

 & Osman (1954). 



Hypotype. P.45527. 



Horizon and locality. Figured specimen, from sample No. 17, W. El- 

 Sharawna section. 



Stratigraphical range. Nakkady (1950) described G. area (Cushman) var. 

 esnehensis from the Maestrichtian Esna shale of the Abu Durba section, western 

 Sinai, Egypt. He also reported it to be frequent in the Maestrichtian Globotruncana- 

 Guembelina Zone of the Abu Durba and Mellaha sections and to flood the Maestrich- 

 tian chalk of Gebel Duwi. 



