186 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



rounded, ovoid, or even angular, weakly or strongly lobate, with or without a single 

 marginal keel which can either be weakly or strongly developed, papillose, nodose, 

 spinose or only thickened and limbate ; axial periphery rounded, subrounded, 

 subacute or acute ; chambers arranged in 2-4 whorls, dextrally or sinistrally coiled ; 

 all chambers seen on dorsal side, only those of last whorl seen on ventral side ; 

 initial chambers generally globular, moderately or strongly inflated ; later ones 

 variable in shape, globular, ovate, lenticular, angular rhomboid or angular conical ; 

 sutures on dorsal side straight or curved, raised or depressed, sometimes thickened, 

 limbate or beaded ; on ventral side sutures generally radial or slightly curved, 

 depressed ; umbilicus varying in shape and size, very small or large, with or without 

 everted umbilical collar and/or high, decorated umbilical shoulders, but always 

 present and open ; aperture interiomarginal, extraumbilical-umbilical, rounded, 

 ovoid or slit-like, sometimes bordered by a lip varying from a narrow rim to a broad 

 flap ; wall calcareous perforate, except for the imperforate keel (where present) ; 

 surface smooth or roughened, papillose, hispid or even spinose. 



Discussion. Cushman (19276) described Globorotalia as a new genus with 

 Pulvinulina menardii (d'Orbigny) var. tumida Brady as the type species. Marie 

 (1941) considered Globorotalia Cushman to have a single terminal aperture, and thus 

 included forms of Globorotalia in which the apertures of the previous chambers 

 remain open into the umbilicus, together with Globotruncana Cushman within his 

 genus Rosalinella (a junior synonym of Globotruncana) despite the marked difference 

 in their apertural characters. 



Cushman & Bermudez (1949) divided Globorotalia largely on the basis of chamber 

 shape into three subgenera, Globorotalia (Globorotalia), G. (Truncorotalia) and G. 

 (Turborotalia) . The first subgenus was characterized by its biconvex, compressed 

 test, angular periphery and small umbilicus ; the second was distinguished by its 

 planoconvex, strongly umbilico-convex test, angular periphery, and peculiarly- 

 shaped apertural face of the last chamber ; the third was separated on the basis of 

 its globular test, rounded periphery and absence of a definite umbilicus. This 

 division of Globorotalia was either partly or completely accepted by various authors, 

 in spite of the fact that chamber shape and the dimension of the umbilicus are 

 characters of specific rather than generic or subgeneric importance, and that all 

 gradations between one extreme and the other have been recorded. Banner & Blow 

 (1959) considered Truncorotalia to be a junior synonym of Globorotalia and Turboro- 

 talia to be a subgenus of the latter. They distinguished Globorotalia (Globorotalia) 

 from Globorotalia (Turborotalia) by the fact that the former has an imperforate 

 peripheral carina, at least in part. Loeblich & Tappan (1964) raised Turborotalia 

 to generic rank, distinguishing it mainly on the basis of its non-carinate periphery. 

 However, it can be demonstrated that representatives of Globorotalia with a rounded, 

 non-carinate periphery evolve gradually into truncated, non-carinate forms, with an 

 acute periphery. These latter, in turn, evolve into sharply keeled Globorotalia 

 through various stages with incipient or partially developed keels. All gradations 

 between each of these forms and the following are documented and show clearly that 

 the division of the present genus into two genera or subgenera (Globorotalia and 



