IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 71 



Bolli, Loeblich & Tappan, Praeglobotruncana Bermudez and Rotalipora Brotzen, all 

 of which differ markedly in their apertural characters. Moreover, a deuteroforamen, 

 such as described by Hofker, had not been recorded in any of the forms he included 

 in his Marginotruncana [e.g. G. marginata Reuss, G. stuarti (de Lapparent), G. contusa, 

 (Cushman), etc.] which conform precisely with the description of the genus 

 Globotruncana as given by Cushman (1927) and emended by later authors. Thus 

 Marginotruncana Hofker is considered a junior synonym of Globotruncana Cushman. 



Reiss (1957) described Globotruncanita as a new genus and distinguished it from 

 Globotruncana Cushman by its chamber form which is mostly polygonal in outline, 

 its entirely single keel, and by its " distinctive apertural characters ". However, as 

 admitted by Reiss, polygonal chambers are also recorded in Globotruncana Cushman. 

 Again, the character of the keel, whether single or double, is of specific importance 

 only within the genus Globotruncana, and cannot be used as a basis for splitting it into 

 two distinct genera. Forms with a double keel are clearly shown in the present 

 study to evolve into single-keeled forms (e.g. G. area -> G. leupoldi), all transitional 

 stages being present. Finally, there is no fundamental difference in the apertural 

 characters of the two genera as described by Reiss (1957) ; both have interiomarginal, 

 umbilical primary apertures, and a cover-plate with accessory apertures. Thus 

 Globotruncanita Reiss is considered a junior synonym of Globotruncana Cushman. 



Reiss also described Globotruncanella and Helvetoglobotruncana as two new genera 

 and stated that Globotruncanella is closely related to Praeglobotruncana, although from 

 his description, it is clearly seen that its apertural characters relate it to Globotruncana 

 not to Praeglobotruncana. However, he distinguished Globotruncanella by its 

 flatly trochospiral test and its undifferentiated keel which never shows any tendency 

 to split into two keels (although his type species was observed in the present study 

 and by Bronnimann & Brown (1956) to have an occasional ventral keel in the last 

 chamber or two) . Otherwise, his description conforms well with that of Globotruncana 

 Cushman. As the degree of flattening of the test and the double- or single-keeled 

 nature of the peripheral band are characters of specific, rather than generic, import- 

 ance, Globotruncanella Reiss is considered a junior synonym of Globotruncana 

 Cushman. 



Similarly Helvetoglobotruncana was only distinguished by its rounded chambers 

 and its subperipheral, monochotamic keel. Again, chamber shape and position of 

 the keel cannot be accepted as generic characters. Forms of Globotruncana with 

 globular chambers and a dorsally-shifted keel (e.g. Globotruncana arabica sp. nov.) 

 are recorded in the present paper, and make the establishment of a new genus impos- 

 sible on the basis of such minor morphological characters. Thus Helvetoglobotruncana 

 Reiss is also considered a junior synonym of Globotruncana Cushman. 



Globotruncana Cushman 1927 is distinguished from Rugoglobigerina Bronnimann 

 1952 by its keel or keels, imperforate peripheral band, less globular chambers and less 

 rugose surface. Trinitella Bronnimann 1952 is transitional in character between 

 Globotruncana and Rugoglobigerina. It can neither be included in the former 

 because it lacks an entire keel and an imperforate peripheral band, nor in the latter 



