IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 231 



Description. Test medium-sized, unequally biconvex, coiled in a low trocho- 

 spire ; dorsal side moderately convex, ventral side strongly and distinctly protruding ; 

 equatorial periphery almost circular, moderately lobate ; axial periphery acute, 

 without keel, but the chambers on the ventral side are so strongly protruding that the 

 marginal periphery appears as if separated from this protruding mass by a very 

 shallow groove in the form of a thick marginal pseudo-keel ; chambers on the dorsal 

 side 18, arranged in 3^ dextrally coiled whorls ; the initial ones are small, inflated, 

 globigerine, almost masked by the surface rugosity and are followed by crescentic, 

 elongated chambers; the last whorl is slightly lower than the preceding whorls, 

 and is composed of 4J, long, narrow, roughly quadrangular chambers, which are 

 strongly elongated in the direction of coiling and increase slowly in size ; on the 

 ventral side the chambers are 4|, large, roughly triangular, conical, moderately 

 inflated and distinctly protruding ; sutures on the dorsal side curved, depressed in 

 the early part, very short, slightly curved and depressed later ; on the ventral side 

 the sutures are straight, radial and strongly incised ; umbilicus relatively small, deep 

 and open ; aperture interiomarginal, extraumbilical-umbilical, a narrow, long arch, 

 with a delicate, narrow lip ; wall calcareous perforate ; surface distinctly papillose, 

 especially in the early part. 



Dimensions of holotype. 



Maximum diameter = 0-35 mm. 



Minimum diameter = 0-30 mm. 



Thickness = 0-29 mm. 



Remarks. Globorotalia pusilla mediterranica has all the main characteristics of 

 the G. pusilla group : the biconvex, strongly inflated test ; the protruding ventral 

 side, with its triangular, conical, high chambers ; radial, depressed ventral sutures ; 

 small umbilicus ; and long, narrow, arched aperture, with an occasional delicate 

 apertural lip. It is thus included as a subspecies of G. pusilla, although it is quite 

 distinct from the other two subspecies, G. pusilla pusilla and G. pusilla laevigata. 

 It differs from the former in protruding more on the ventral side, in having a higher 

 umbilical shoulder, a thick, marginal pseudo-keel, and quadrangular chambers on 

 the dorsal side. From the latter it is distinguished by its more convex dorsal side, 

 greater protrusion of the ventral surface, its thick marginal pseudo-keel, rough 

 surface, and the shape of the chambers on the dorsal side. 



Globorotalia pusilla mediterranica is believed to have evolved from G. pusilla 

 pusilla, but nothing is known as yet about its evolution in younger strata, as no 

 morphologically similar forms have so far been described. 



Holotype. P.45624. 



Paratypes. P. 45625. 



Horizon and locality. Holo- and paratypes, from sample No. 37, Gebel 

 Owaina section. 



Stratigraphical range. Globorotalia pusilla mediterranica appears in the upper 

 part of the G. pusilla Subzone of upper Middle Paleocene age. It continues 



