236 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



Globorotalia tribulosa Loeblich & Tappan 

 (PI. 18, figs. 2a~c) 

 1957a Globorotalia tribulosa Leoblich & Tappan : 195, pi. 56, figs. 3<z-c ; pi. 61, figs. ja-c. 



Description. Test medium-sized, globular, inflated, coiled in a very low trocho- 

 spire ; dorsal side flat in the early part, inflated later ; ventral side strongly inflated ; 

 equatorial periphery roughly quadrate and distinctly lobate ; axial periphery 

 rounded ; chambers on the dorsal side about 12-14, arranged in 2| dextrally coiled 

 whorls ; initial chambers very small, much flattened and almost masked by the 

 surface rugosity ; the last whorl is composed of 4 large globular chambers which 

 increase so rapidly in size that the last two chambers constitute most of the test ; on 

 the ventral side the 4 chambers are also strongly inflated ; sutures on the dorsal side 

 curved, depressed in the early part, almost straight, radial and depressed later ; on 

 the ventral side they are radial and strongly incised ; umbilicus small, deep and open ; 

 aperture a large, crescentic arch, interiomarginal, extraumbilical-umbilical ; wall 

 calcareous, perforate ; surface distinctly papillose, with the papillae sometimes 

 tapering out to form fine, delicate spines giving the surface a hispid appearance. 



Dimensions of described specimen. 

 Maximum diameter = 0-40 mm. 

 Minimum diameter = 0-22 mm. 



Thickness = 0-24 mm. 



Remarks. Globorotalia tribulosa is distinguished from G. pseudobulloides (Plum- 

 mer), from which it probably evolved, by its rough, papillose and hispid surface. 

 It differs from G. esnaensis (Le Roy) in having a more globular, lobate test, chambers 

 which increase more rapidly in size, a characteristic large aperture and by the fact 

 that its surface is not as rough as that of G. esnaensis. G. tribulosa appears to be 

 transitional between G. pseudobulloides and G. esnaensis. 



Hypotype. P.45630. 



Horizon and locality. Figured specimen from sample No. 32, Gebel Owaina 

 section. 



Stratigraphical range. Loeblich & Tappan (1957a) described G tribulosa 

 from the Nanafalia formation of Alabama and the Aquia formation of Virginia 

 which they considered as lower Eocene (Ypresian) and Upper Paleocene (Landenian) 

 respectively. However, both Bramlette & Sullivan (1961) and Gartner & Hay 

 (1962) considered the Nanafalia formation to be of Upper Paleocene age. 



In the Esna-Idfu region G tribulosa appears in the uppermost part of the Danian 

 and continues as a common form throughout the overlying Middle Paleocene. It dies 

 out completely in the basal part of the uppermost Paleocene, G. aequa/G. esnaensis 

 Subzone. 



Globorotalia trinidadensis Bolli 



(PI. 18, figs, ja-c) 



1957b Globorotalia trinidadensis Bolli : 73, pi. 16, figs. 19-23. 



19606 Globorotalia trinidadensis Bolli : Bolli & Cita : 29-30, pi. 33, figs. la-c. 



