IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 181 



Stratigraphical range. The species was first described from the basal part of 

 the upper Midway group of Texas, which, according to Loeblich & Tappan (1957a), 

 is of Upper Danian age. Plummer (1926 : 135) stated that the species is rare in the 

 lower Midway becoming most common in the basal part of the upper Midway, and 

 that it aids in marking the Cretaceous-Tertiary boundary, as no similar form has been 

 seen in the Cretaceous strata below. In spite of this early precise remark of Plum- 

 mer, many authors (e.g. Said & Kerdany 1961 ; Hofker 1960^, i ; Nakkady 1959 ; 

 Khalilov 1948, 1949 ; White, 1928) have recorded G. triloculinoides or its synonyms 

 from rocks of Maestrichtian age. Clearly, these authors confused G. triloculinoides 

 with the superficially similar Maestrichtian Rugoglobigerina forms of the macrocephala 

 group. 



Troelsen (1957) and Berggren (19606, 1962) recorded G. triloculinoides as rare in the 

 lower part of the Middle Danian at its type locality in Denmark, and in southern 

 Scandinavia, becoming more common towards the Upper Danian Tylocidaris 

 vexilifera Zone ; they did not record it from the Lower Danian. 



Berggren (1962 : 88) added that " it does not seem to occur in the Thanetian 

 glauconites above in southern Scandinavia (unless it be in subsurface sections in 

 Denmark), but its continued development elsewhere in more favourable fades is well 

 documented ". 



Haynes (1955, 1956) recorded G. triloculinoides from the type Thanetian of 

 England, and it was identified from recently studied Thanetian samples which were 

 kindly given to the present author by Dr. Haynes. 



Bolli (19576) recorded G. triloculinoides throughout the lower part of the Paleocene 

 lower Lizard Springs formation of Trinidad. However, Bolli's G. triangularis White, 

 which he recorded throughout the whole Paleocene, is probably G. triloculinoides 

 Plummer. 



Loeblich & Tappan (1957a), after a study of different Lower Tertiary sections 

 including the type locality of G. triloculinoides, showed that it ranges throughout the 

 whole Paleocene, but dies out completely before the basal Eocene. 



Hay (i960) recorded G. triloculinoides throughout the whole Paleocene Velasco 

 formation of Mexico, it being most abundant in the Lower Paleocene (Danian). 



Khalilov (1948, 1949), Subbotina (1953), Gans & Knipscheer (1956), Said (i960) 

 and Kupper (1961) extended the range of G. triloculinoides to strata younger than the 

 Paleocene. These authors apparently confused G. triloculinoides with its younger 

 descendants. 



In the Esna-Idfu region, G. triloculinoides Plummer floods the whole Paleocene 

 section from the Upper Danian onwards (the Lower and Middle Danian being missing) 

 and dies out completely at the top of the Upper Paleocene Globorotalia velascoensis 

 Zone, and thus is considered one of the best Paleocene index fossils. All reliable 

 references record G. triloculinoides from Paleocene strata in various parts of the 

 world. 



