216 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFER A 



Remarks. Specimens of G. imitata Subbotina from the Esna-Idfu region con- 

 form well with the original description and figures, although the specimen figured 

 here is slightly larger, has subglobular rather than oval chambers, and has more 

 chambers in the final whorl. However, as mentioned by Subbotina, such minor 

 differences fall well within the range of variation of the species. 



G. imitata was described by Subbotina as having a close resemblance both to 

 G. membranacea and G. compressa (Plummer). However, Subbotina's G. membran- 

 acea included representatives of G. compressa, G. ehrenbergi and G. pseudomenardii, 

 all of which are morphologically and stratigraphically distinct from G. imitata. 

 The latter species is believed to have evolved from G. pseudobulloides (Plummer) by 

 reduction in the size of test and rate of chamber growth, by flattening of the dorsal 

 side and the development of a smooth test. However, it might have evolved from 

 G. compressa although no direct evidence was found. G. imitata probably evolved 

 into G. ehrenbergi Bolli, by the development of a slightly more compressed test and 

 a weak keel on the last chamber. Forms of G. ehrenbergi without the partially 

 developed keel are believed to be transitional to G. imitata. 



Said (i960) and Said & Kerdany (1961) described as G. imitata Subbotina (from 

 the Lower Eocene Thebes limestones of Luxor and the Upper Paleocene Esna shales 

 of Farafra Oasis respectively) forms which are completely different from Subbotina's 

 original description and figures. Said's form was recorded as ranging through the 

 Lower Eocene only, whereas G. imitata was first described from the Danian and was 

 found to die out completely long before the Lower Eocene. Said relied on Loeblich 

 & Tappan's record of G imitata from the Nanafalia formation of Alabama which they 

 considered as Lower Eocene, but both Bramlette & Sullivan (1961) and Gartner & 

 Hay (1962) assigned this formation to the Paleocene. 



Hypotype. P. 4561 1. 



Horizon and locality. Figured specimen, from sample No. 7, Gebel El- 

 Kilabiya section. 



Stratigraphical range. The species was first described by Subbotina (1953) 

 from the zone of " Rotalia-like Globorotalia " , Elburgan horizon, Northern Caucasus, 

 which she tentatively assigned to the Danian. It was also recorded from the Danian 

 of the Gulf and Atlantic Coastal Plains of the U.S.A., where it was found to continue 

 through the overlying Landenian and the so-called Lower Eocene (Loeblich & 

 Tappan 1957a ; Olsson i960). 



In the Esna-Idfu region G. imitata occurs as a rare to common form in the Upper 

 Danian (the Lower and Middle Danian being missing), and continues as a rare form 

 up to the basal part of the Upper Paleocene G. velascoensis Zone. 



Globorotalia irrorata Loeblich & Tappan 

 (PI. 23, figs, ga-c) 

 1957a Globorotalia irrorata Loeblich & Tappan : 191, pi. 46, figs. ia~c ; pi. 6i, figs. ^a-c. 



Description. Test medium sized, coiled in a low trochospire ; dorsal side almost 

 flat, weakly inflated ; ventral side strongly inflated ; equatorial periphery roughly 



