70 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



(1927, 1928) and emended by later authors. Thus Rosalinella Marie 1941 is consid- 

 ered a junior synonym of Globotrnncana Cushman 1927. 



Reichel (1950) divided the genus Globotrnncana into four subgenera : Globotrnncana 

 s.s., Rotalipora Brotzen, Thalmanninella Sigal and Ticinella Reichel. However, the 

 apertural characters of the last three genera are different from those of Globotrnncana 

 Cushman and they were therefore considered separately by Sigal (1952), Bolli, 

 Loeblich & Tappan (1957) and Banner & Blow (1959). 



Gandolfi (1955) added a fifth subgenus to Reichel's classification, considering 

 Rngoglobigerina Bronnimann as a subgenus of Globotrnncana Cushman. However, 

 the absence of true keels and a peripheral band, the constant presence of well-develop- 

 ed surface rugosity, and the fact that the two forms have not yet been proved to 

 grade into one another, favour the consideration of Rngoglobigerina as a separate 

 genus. 



Bronnimann & Brown (1956) described Rugotruncana as a new genus. They 

 distinguished it from Globotrnncana by the fact that "... some or all later chambers 

 exhibit fine discontinuous costellae or traces of costellae.", otherwise their descrip- 

 tions of the two genera are identical. However, as previously mentioned by Bolli, 

 Loeblich & Tappan (1957), surface ornamentation alone cannot be used as a generic 

 character, and thus Rogotmncana should be considered a junior synonym of Globo- 

 trnncana, although Banner & Blow (1959) considered it as a subgenus of the latter. 

 Forms of Globotrnncana with a highly roughened surface are recorded, and variation 

 of the surface rugosity within the same species population renders generic or sub- 

 generic distinction impossible on this basis alone. Moreover, Bronnimann & Brown 

 (1956) included Abathomphalus intermedia (Bolli) and A. mayaroensis (Bolli) within 

 Rugotruncana, in spite of the difference in the apertural characters of the two genera. 

 They also described Bucherina as a monotypic genus. They stated that it resembles 

 Globotrnncana and Rugotruncana, but differs from both " in lacking an umbilical 

 cover-plate and in exhibiting a shift in the axis of coiling ". They further stated 

 that " short apertural flaps extend into the umbilicus but do not form a cover-plate". 

 However, as mentioned above, the cover-plate is a very delicate structure which is 

 rarely well-preserved, and the shift in the axis of coiling is not a generic character. 

 The establishment of a new genus on such a weak basis cannot be accepted, and 

 Bucherina Bronnimann & Brown is therefore considered a junior synonym of 

 Globotrnncana Cushman. Again, these authors stated that Globigerina mckannai 

 White may possibly belong to their new genus Bucherina. However, no apertural 

 flaps were ever observed in G. mckannai, which is a true Globigerina, recorded only 

 from the Upper Paleocene and Lower Eocene, where no globotruncanid-like forms 

 are known. 



Hofker (1956) proposed Marginotruncana as a new genus. He distinguished it 

 from Globotrnncana Cushman on the basis of a so-called strongly reduced primary 

 aperture (protoforamen) in the latter, which is either completely lost or fused with 

 a secondary aperture (deuteroforamen) in the former. He included within Margino- 

 truncana, forms which actually belong to Globotrnncana Cushman, Abathomphalus 



