Diagnosis - A Rugoglobigerina (Rugoglobigerina) species distinguished by its small to medium sized, low trochospiral, quadrate test; 4-4Yz regularly increasing or only very slowly increasing cham-bers in the outer whorl and rapidly increasing chambers in the inner one; depressed spiral suture and radial, incised intercameral ones; small umbilicus and delicate distinctly developed meridional costellae.

Description - Test medium-sized, coiled in a low trochospire; dorsal side almost flat to slightly concave with a depressed inner part and inflated later chambers; ventral side inflated, protruding; equatorial periphery quadrate, lobate; axial periphery rounded; chambers on the dorsal side 11, arranged in 2 dextrally coiled whorls; the initial chambers are small, globigerine and inflated; they increase regularly in the early part until the beginning of the second whorl when the rate of increase is somewhat decelerated; the outer whorl is composed of 4, globigerine, inflated chambers which increase regularly in size as added; the last chamber is somewhat elongated in the direction of coiling; on the ventral side, the chambers are 4, globigerine, inflated and increase regularly in size; spiral suture depressed; inter-cameral sutures on both sides almost straight, radial and depressed, more so on the ventral side where the 4, depressed sutures join the umbilical periphery in a cross form; umbilicus small, covered by a complex system of tegilla of which remnants are still preserved; primary aperture interiomarginal umbilical covered by tegilla, remnants of which are still preserved; surface rugose covered by well developed meridional costellae which are somewhat reduced on the last chamber; wall calcareous, perforate, hyaline; except for the imperforate tegilla and surface rugosity.

Remarks. - Rugoglobigerina (R.) browni El-Naggar is distinguished from the morphologically similar Rugoglobigerina ( R.) rugosa (Plummer) [Globigerina rugosa, 1927] by its smaller, thinner, quadrate test, much narrower umbilicus, and less rugose surface. From R. (R.) macrocephala it is distinguished by its less rapid rate of chamber growth in the outer whorl; a much smaller last chamber, which can be either larger or smaller than the penultimate one; its quadrate appearance, more or less perpendicular sutures on the ventral side, smaller umbilicus and rougher surface. From R. (R.) ornata it can be easily separated by the above mentioned characters as well as by its less developed surface rugosity.

Stratigraphical range - Rugoglobigerina (R.) browni is common in the Middle and Late Maastrichtian rocks of the Esna-Idfu region, Nile Valley, Egypt, U. A. R.

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