ABSTRACT: Nummulites mihashamensis n. sp., typical of the N. laevigatus group, is biometrically studied, described and illustrated through both generations from a limestone bank of the upper LutetianMidawara Formation of Gebel El Mihasham, recorded from east Beni Mazar,NileValley, Egypt.Detailed investigations of the new species: N. mihashamensis n. sp. and its ontogenetic growth stages are discussed. The biometric analysis demonstrated that N. mihashamensis n. sp. lies phylogenetically in parallel Lineage to that of N. crassichordatus Boukhary et al. 2010. Both species are chronostratigraphically coeval, assigned to a Late Lutetian age, (SBZ 16 of Serra-Kiel et al. 1998, PZ P12A, 42.3 â€“ 40.2Ma, see BouDgher-Fadel 2013). N. crassichordatus fromMokattam is considered to be the ancestral species of N. bartovigatus Boukhary and Hussein 2002 from Helwan. To compare species of N. laevigatus group phylogenetically, Nummulites mihashamensis n. sp., N. crassichordatus and N. bartovigatus are useful in the southern Tethys for age dating compared with those in northern Tethys of Schaub 1981. It is evident that there is speciation between the northern and southern Tethys ocean as Nummulites are bottom dwellers that could not cross this deep basin, the connection of these species wasmore likely through the shallow shelves.