IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 177 



apertural lip of which remnants are still preserved ; wall calcareous, perforate ; 

 surface heavily papillose or even nodose. 



Dimensions of described specimen. 

 Maximum diameter = 0-33 mm. 

 Minimum diameter = 0-25 mm. 



Thickness = 0-25 mm. 



Remarks. Globigerina stonei is distinguished by its small to medium sized, 

 moderately inflated test ; its very small, tightly coiled, depressed early part, and 

 relatively large, strongly inflated chambers which increase rapidly in size in the last 

 whorl, and have almost straight, depressed, inner margins and distinctly curved 

 outer ones ; its radial, depressed sutures on both sides ; its angular, depressed spiral 

 suture, and its papillose or rather nodose surface. 



Acarinina triplex Subbotina (1953, pi. 23) includes forms identical with both G. 

 stonei (figs. 1, 3, 5) and G. velascoensis (figs. 2, 4). However, examination of the 

 holotypes is needed before using the name G. triplex for G. stonei. 



Berggren (1960a) removed Acarinina triplex Subbotina to Globigerina as he noticed 

 that the aperture is interiomarginal, umbilical in position and sometimes extends 

 towards the periphery. He stated that he had compared his specimens of Globi- 

 gerina triplex (Subbotina) from the Lower Eocene of Denmark and northwestern 

 Germany with comparative material in the collection of Dr. N. Subbotina, Leningrad, 

 and found them to be identical. However, his figured forms (pi. 6, figs. 2a~3c, 

 pi. 13, figs, \a-2c) differ from both Acarinina triplex Subbotina and G. stonei Weiss, 

 in having a higher dorsal side, more spinose surface, and in lacking the straight 

 inner margins of the chambers and the angular spiral suture. 



Subbotina (1953) also described as Globigerina pseudoeocaena var. trilobata, a form 

 which probably belongs to G. stonei, although it is much larger. 



Bolli (1957&) described as Globigerina primitiva (Finlay), forms which most 

 probably belong to G. stonei Weiss, as can be seen from his figures. Globoquadrina 

 primitiva was first described by Finlay (1947) from the Middle Eocene of New 

 Zealand, but was removed to the genus Globigerina by Bronnimann (1952&). Exam- 

 ination of topotypes of Globoquadrina primitiva Finlay kindly sent to the present 

 author by Drs. N. de B. Hornibrook and G. Jenkins of the Geological Survey of New 

 Zealand, showed that it is quite distinct from the present species, although it has a 

 similarly rough surface, a straight, depressed spiral suture and a quadrate appearance. 

 In view of these morphological similarities, it is possible that G. stonei evolved into 

 Globoquadrina primitiva in Lower Eocene time by the development of the character- 

 istic apertural flaps, the peculiar apertural face of the last chamber and the angularly 

 protruding ventral side. On the other hand, G. stonei is believed to have evolved 

 from G. velascoensis Cushman in Upper Paleocene time by the development of the 

 rough surface and non-appressed last chamber. Specimens of G. stonei with a finely 

 papillose surface are believed to be transitional to G. velascoensis, while those with 

 the heavily nodose surface are probably transitional to G. primitiva. 



Gartner & Hay (1962) described as G. cf. G. inaequispira Subbotina from the type 



