IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 155 



pretendues Globigerina, mais etant donne que nous n'avons jamais trouve trace de 

 passage dans notre materiel ou dans le materiel publie, nous devons nous considerer 

 comme obliges de separer taxinomiquement ce groupe de Globigerina et de lui donner 

 un nouveau nom de genre : Subbotina n.gen." However, both Hofker (1960^, i) and 

 Berggren (1962) suggested the development of Globigerina triloculinoides Plummer, 

 from Globorotalia pseudoballoides (Plummer), a species with a very finely pitted 

 surface, which is believed to have evolved from forms with a smooth, finely perforate 

 surface (see Berggren 1962 : 90). Again, G. triloculinoides Plummer is believed to 

 have evolved into G. inaequispira Subbotina, a species with a less reticulate surface. 

 Moreover, the surface texture in the various species of Globigerina varies from smooth, 

 to hispid, papillose, nodose, spinose, pitted or reticulate. Variation in the surface 

 texture from one species to another, and amongst members of the same species 

 excludes the possibility that this feature alone can be used as a generic character. 

 Thus the separation of globigerinas with a reticulate surface as a distinct genus 

 cannot be accepted without a complete study of the various forms of surface texture 

 and of their relationship to each other through the various evolutionary lineages in 

 Globigerina. It is believed that different types of surface texture grade imper- 

 ceptibly into one another. The suggested lineages in Globigerina (Text-fig. 13) show 

 the gradual evolution of highly spinose, nodose forms from smooth-surfaced ones. 

 Thus Subbotina Brotzen & Pozaryska 1961 is here considered a junior synonym of 

 Globigerina d'Orbigny 1826. 



Loeblich & Tappan (1964) emended the diagnosis of Subbotina, adding that the 

 aperture is umbilical-extraumbilical, and stating that " The coarsely pitted surface 

 is found in species with low and slightly extraumbilical aperture and distinctive lip, 

 none of which is found in typical Globigerina." However, most Globigerina species 

 show a slight tendency towards the extension of the aperture to a somewhat extra- 

 umbilical position, but not as much as in true Globorotalia. Again, variation in the 

 degree of elevation of the dorsal side, in the development of the apertural lip, and in 

 surface texture are characters of specific, rather than generic importance. Moreover, 

 Subbotina was described as having the same stratigraphical range as Globigerina 

 d'Orbigny. 



Remarks. Eighteen species and subspecies of Globigerina are described in the 

 present study, four species and one subspecies of which are new. These new forms 

 are: Globigerina alanwoodi sp.nov., G. arabica sp.nov., G. haynesi sp.nov., G. nodosa 

 sp.nov., and G. triloculinoides parva subsp.nov. 



Evolutionary Development of globigerina 



The genus Globigerina was always thought to be the ancestral stock from which 

 most globigerinids evolved, because its range was wrongly considered to be Upper 

 Jurassic to Recent. However, as explained earlier, the Mesozoic records are probably 

 incorrect. Moreover, the widespread faunal break between the Maestrichtian and 

 the Danian makes it difficult to follow the early evolutionary development of the genus. 

 Whether Globigerina has evolved from Rugoglobigerina by the loss of the tegilla and 

 the meridional costellae, from Hedbergella by the confinement of the aperture to an 



