248 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



form well with G. velascoensis velascoensis (Cushman) although the ventral side is 

 more protruding. Variation in the degree of protrusion of the ventral side in 

 G. velascoensis velascoensis is clearly documented in the present study (e.g. PL 21, 

 fig. 3) and proves G. crater Finlay to be a junior synonym. Examination of topotypes 

 of G. crater Finlay, kindly sent to the present author by Drs. N. de B. Hornibrook 

 and G. Jenkins of the New Zealand Geological Survey, showed its identity with 

 G. velascoensis velascoensis (Cushman) in spite of minor differences which fall well 

 within the range of variation of the latter. 



Haynes (1955, 1956) described as Globorotalia velascoensis (Cushman) aff. var. 

 acuta (Toulmin), from the type Thanetian of England, a reworked Upper Cretaceous 

 Globotruncana species. This record of Haynes was used by various authors (e.g. 

 Loeblich & Tappan 1957a, b ; Bolli & Cita 1960a, b ; etc.) as a basis for considering 

 the G. velascoensis Zone to be of Thanetian age. However, Globorotalia velascoensis 

 (Cushman) was neither observed in the collection of Dr. Haynes, nor in the various 

 type Thanetian samples, recently collected by the present author. 



Bolli (1957&) included G. acuta Toulmin in the synonymy of G. velascoensis (Cush- 

 man), while Loeblich & Tappan (1957a) considered them separately. 



Globorotalia velascoensis velascoensis (Cushman) is distinguished by its large, 

 planoconvex, strongly umbilico-convex test ; its characteristic umbilical collar ; 

 well-developed, beaded keel ; curved, raised, beaded, dorsal sutures and radial, 

 incised ventral ones ; its smooth surface ; large, deep umbilicus and characteristic 

 aperture. It is believed to have evolved from G. angulata abundocamerata Bolli into 

 its two other subspecies as well as into G. bollii sp. nov. and G. formosa gracilis Bolli. 

 This is substantiated by the morphological characters and stratigraphical distribution 

 of these forms, and by the occurrence of several transitional stages. 



Hypotypes. P.45640-41. 



Horizon and locality. Figured specimens, PL 20, figs, ^a-d, from sample No. 

 41, and PL 21, fig. 3, from sample No. 37, Gebel Owaina section. 



Stratigraphical range. Globorotalia velascoensis velascoensis (Cushman) is one 

 of the finest known Upper Paleocene index fossils. It has been recorded from 

 practically every part of the world where rocks of this age have been studied. It 

 characterizes and is restricted to the G. velascoensis Zone (uppermost Paleocene), 

 although some authors have wrongly extended its range to the Middle Eocene, and 

 others have considered the zone to fall entirely within the Lower Eocene. The 

 dispute over the stratigraphical position of the zone does not lessen the value of 

 G. velascoensis in stratigraphical correlation, although misidentification of the species 

 and confusion with other species has thrown some doubt on its true stratigraphical 

 range. Nevertheless, all reliable records show that G. velascoensis velascoensis 

 (Cushman) is restricted to the Upper Paleocene, and that records of this species from 

 older or younger strata are erroneous. 



In the Esna-Idfu region, G. velascoensis velascoensis floods the upper part of the 

 Paleocene, constituting a distinct faunal zone, the G. velascoensis Zone. The first 



