84 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



Description. (PI. i, figs. za-c). Test large, robust, unequally biconvex, coiled 

 in a relatively high trochospire ; dorsal side convex, broadly arched, ventral side 

 moderately inflated, slightly protruding ; equatorial periphery subcircular, moder- 

 ately lobate ; axial periphery angular, slightly truncate, with two well-developed, 

 strongly thickened marginal keels ; chambers on the dorsal side 22, arranged in 3^ 

 dextrally coiled whorls ; the initial ones are small, inflated, globigerine, increase very 

 slowly in size and are followed by typically crescentic chambers ; the last whorl is 

 composed of 7 (6+1 abortive), large, typically crescentic chambers (except for the 

 fourth and fifth) which increase slowly in size ; on the ventral side these chambers 

 are subglobular to ovoid, moderately inflated, sharply outlined by distinctly thicken- 

 ed horseshoe-shaped ridges ; sutures on the dorsal side curved, raised, thickened and 

 beaded except on both sides of the antepenultimate chamber where they tend to be 

 almost straight ; on the ventral side the sutures are short, thickened, raised, beaded 

 and slightly curved forward ; umbilicus roughly hexagonal in outline, wide, deep, 

 surrounded by raised ridges and covered by complex tegilla of which remnants are 

 still preserved ; primary apertures interiomarginal, umbilical ; tegilla with accessory 

 apertures only poorly preserved ; wall calcareous, perforate except for the imperfo- 

 rate keels, peripheral band and tegilla ; surface smooth except for a few small, 

 scattered papillae ; the two subparallel keels are well-developed, limbate and beaded, 

 they enclose a relatively wide, depressed, inclined peripheral band except on the last 

 chamber where the two keels become closer to each other ; the dorsal keel is more 

 developed and strongly protruding while the ventral keel is slightly shifted towards 

 the inner part of test. 



Dimensions of described specimen. 



Maximum diameter = 0-52 mm. 



Minimum diameter = 0-46 mm. 



Thickness = 0-27 mm. 



Main variation. 



1. Chambers on the dorsal side 18-24, arranged in 3-4 whorls, generally dextrally 



coiled. 



2. The last whorl is composed of 5-8 chambers, but 6-7 is most common. 



Remarks : Globotruncana area (Cushman) was first described by Cushman (1926) 

 as Pulvinulina area n.sp. He later (1927) erected Globotruncana as a new genus, with 

 Pulvinulina area Cushman 1926, as type species. 



Plummer (1931) described as G. area, double- and single-keeled forms which 

 differ from Cushman's original description and figures. Bronnimann & Brown 

 (1956 : 450) stated that " Her two-keeled forms are specimens of Git. cretacea 

 Cushman which is an incipient Git. rosetta (Carsey). Her one-keeled forms are 

 actually double-keeled, but the two keels are very close together ; they are well- 

 developed specimens of Git. rosetta." 



Cushman (1932) described as G. area, a planoconvex, single-keeled form, and in 

 1946 he presented the figures of the holotype and of this form as G. area. Cita (1948) 



