J5o UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



G. wilcoxensis Cushman & Ponton by the development of the sharply acute axial 

 periphery of the last chamber, and by the increase in surface rugosity. 



Hypotype. P. 45642. 



Horizon and locality. Figured specimen, from sample No. 55, Gebel Owaina 

 section. 



Stratigraphical range. The species was described by Weiss (1955a, b) from 

 the Paleocene and Lower Eocene of northwestern Peru. It was previously recorded 

 by White (1928) from the Tampico Embayment of Mexico, where he described its 

 range as being Upper Cretaceous-Paleocene. He certainly confused it with 

 superficially similar Globotruncana or Hedbergella species in the Upper Cretaceous 

 rocks below, and thus obscured its range. G. whitei was also recorded from the Lower 

 Eocene of Venezuela (Nuttall 1935), the Lower Eocene Globorotalia rex Zone of the 

 upper Lizard Springs formation of Trinidad (Bolli 19576) and from the lowermost 

 Eocene of the Sylvania guyot, Mid-Pacific (Hamilton & Rex 1959). 



In the Esna-Idfu region G. whitei occurs as a common to abundant form in the 

 uppermost Paleocene G. aequa-G. esnaensis Subzone. It crosses the Paleocene- 

 Lower Eocene boundary and dies out in the overlying G. wilcoxensis Zone. 



Globorotalia wilcoxensis Cushman & Ponton 

 (PL 23, figs. 5«-c) 



1932 Globorotalia wilcoxensis Cushman & Ponton : 71, pi. 9, figs, loa-c. 



J 939 Globorotalia wilcoxensis Cushman & Ponton ; Cushman & Garrett : 88, pi. 15, figs. 21, 22. 



1944 Globorotalia wilcoxensis Cushman & Ponton ; Cushman : 15, pi. 2, figs. 14, 15. 



1948 Globorotalia wilcoxensis Cushman & Ponton ; Cushman & Todd : 36, pi. 6, figs. 24, 25. 



1948 Globorotalia wilcoxensis Cushman & Ponton ; Shifflett : 73, pi. 40, figs. 20-22. 



1949 Globorotalia (Truncorotalia) wilcoxensis Cushman & Ponton ; Cushman & Bermudez : 

 39, pi. 7, figs. 16-18. 



1953 Globorotalia wilcoxensis Cushman & Ponton 



1955a Globorotalia wilcoxensis Cushman & Ponton 



1955b Globorotalia wilcoxensis Cushman & Ponton 



1958 Globorotalia wilcoxensis Cushman & Ponton 



Hamilton : 231, pi. 32, fig. 7. 

 Weiss : 19, pi. 6, figs. 7-9. 

 Weiss : 308, pi. 1, figs. 24, 25. 

 Asano : 46, pi. 12, figs. /\a-c. 



Description. Test medium-sized, planoconvex, coiled in a very low trochospire ; 

 dorsal side flat, slightly compressed, ventral side inflated, protruding ; equatorial 

 periphery roughly ovoid, distinctly lobate ; axial periphery subrounded to subangular 

 in the early part, angular in the later part; chambers on the dorsal side about 9, arrang- 

 ed in 2 dextrally coiled whorls ; the initial chambers are small, almost masked by the 

 surface rugosity and are followed by large, crescentic, overlapping chambers which 

 increase moderately in size ; the last whorl is composed of 4, large, roughly ovoid 

 chambers, which are elongated in the direction of coiling, and increase slowly and 

 regularly in size, except for the last which is slightly smaller than the penultimate ; 

 on the ventral side the chambers are 4, large, subglobular and strongly inflated ; 

 sutures on the dorsal side curved, depressed ; on the ventral side they are straight, 

 radial and strongly incised ; umbilicus small, deep and open (although in the figured 

 specimen the last chamber is strongly pushed over the umbilicus) ; aperture interio- 



