IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 171 



1962 Globovotalia (Acarinina) mckannai (White) ; Hillebrandt : 140-141, pi. 14, figs. 



8a-ioc. 

 1962 Globovotalia {Acarinina) pentacamerata Subbotina ; Hillebrandt : 142, pi. 14, figs. ya-c. 



Description. Test large, coiled in a low trochospire ; dorsal side very slightly 

 raised, moderately inflated, ventral side highly raised and strongly inflated ; equa- 

 torial periphery subcircular, distinctly lobate ; axial periphery rounded ; chambers 

 on dorsal side 19, arranged in 3 dextrally coiled whorls ; the initial chambers are 

 small, globigerine, and are followed by slightly larger, roughly globular chambers 

 which increase moderately and regularly in size ; the last whorl is composed of 6 

 large, roughly globular chambers which are slightly elongated in the direction of 

 coiling and which increase regularly in size up to the fourth chamber and then become 

 gradually smaller ; on the ventral side the 6 roughly globular, strongly inflated 

 chambers increase moderately and regularly in size at first, but after the fourth 

 become smaller ; sutures on the dorsal side curved, depressed in the early part, very 

 slightly curved to almost straight, depressed in the later part ; on the ventral side the 

 sutures are almost straight, radial and strongly incised ; umbilicus wide, deep and 

 open ; aperture interiomarginal, umbilical ; wall calcareous, perforate ; surface 

 distinctly granular, papillose or even nodose, with the nodes tapering out in the form 

 of short, stout, spine-like projections especially along the periphery and around the 

 umbilicus. 



Dimensions of described specimen. 



Maximum diameter = 0-45 mm. 



Minimum diameter = 0-34 mm. 



Thickness = 0-28 mm. (across the middle part test) 



Remarks. White (1928) noticed that the aperture in G. mckannai extends from 

 the umbilicus approximately half way to the peripheral margin. This feature has 

 since made it difficult for authors to decide whether the species is a true Globigerina 

 or a Globovotalia. 



Bolli (19576), followed by Bolli & Cita (19606), Hillebrandt (1962) and Gartner & 

 Hay (1962), removed this species to the genus Globorotalia, while Loeblich & Tappan 

 (1957a) and Berggren (1960a), emphasized the fact that it is a true Globigerina, 

 although the aperture in some specimens shows a tendency to extend to a somewhat 

 extraumbilical position. The present study substantiates these observations, and 

 specimens of G. mckannai with typical interiomarginal, umbilical apertures were 

 recorded in far greater numbers than forms with a slight tendency towards the devel- 

 opment of an extraumbilical aperture. Moreover, the forms described by Bolli 

 (19576) as Globorotalia mckannai (White) differ from the holotype in being smaller, 

 higher on the dorsal side and having a much narrower umbilicus. On the other 

 hand, Bolli (pi. 16, figs. 1-3, 10-12) described as G. gravelli Bronnimann and as a 

 transitional form between G. soldadoensis and G. gravelli, forms which are typically 

 G. mckannai. 



Nakkady (1950) described as Globigerina cretacea var. esnehensis, a form which is 

 typically G. mckannai. Examination of the holotype of Nakkady (B.M.N.H., 



