222 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



figs. 4<i-c), also described as G. angulata (White), forms which most probably belong 

 to G. occlusa. 



Bolli & Cita (1960b) described as G. acutispira a form which only differs from the 

 present species in being slightly more lobate : it is thus included in the synonymy. 



Hillebrandt (1962) considered G. occlusa as a subspecies of G. velascoensis, but the 

 present study showed clearly that the two species should be considered separately in 

 spite of their morphological similarity. 



Globorotalia occlusa is distinguished by its medium-sized, umbilico-convex test ; 

 weakly curved dorsal side and protruding ventral side ; its very narrow, deep 

 umbilicus ; papillose umbilical shoulder, thin, papillose or even hirsute keel ; 

 slightly rough early part ; curved, raised, delicately beaded dorsal sutures and radial 

 strongly depressed, ventral ones. It is believed to have evolved from G. angulata 

 (White) as indicated by their morphological characters and stratigraphical distri- 

 bution, although no direct evidence was recorded. On the other hand, G. occlusa 

 is morphologically somewhat similar to G. aragonensis Nuttall, which may be among 

 its direct or indirect descendants. 



Globorotalia occlusa is also morphologically similar to G. simulatilis (Schwager), 

 although very little is known about this form. However, G. occlusa has a distinctly 

 developed marginal keel, while Schwager (1883) in his original description oiDiscorbina 

 simulatilis stated that " the test is somewhat drawn out towards the periphery, but 

 in no way really keeled ". Nevertheless, Said (i960) described as G. simulatilis 

 (Schwager) from the " Esna shales " of Luxor section, Egypt, a form with a distinctly 

 developed marginal keel as can be seen from his figures. This form is possibly G. 

 subbotinae Morozova. Said relied on his study (Said & Kerdany 1961) of supposed 

 topotype material of Schwager's species, but the form figured by these authors also 

 has a distinct marginal keel. It was described from the Upper Paleocene G. velasco- 

 ensis Zone while Schwager's holotype is from the Lower Eocene " Libysche Stufe ". 



Hypotypes. P. 45618-19. 



Horizon and locality. Figured specimens, PI. 20, figs. 2a-d, PL 22, figs. 

 4«-c, from samples No. 40 and 51 respectively, Gebel Owaina section. 



Stratigraphical range. Loeblich & Tappan (1957a) described the holotype of 

 G. occlusa from the Paleocene Velasco formation of Mexico. They also recorded 

 the species from the Upper Landenian (Sparnacian) Vincentown formation of New 

 Jersey, Salt Mountain limestone of Alabama and the Aquia formation of Virginia. 



Bolli & Cita (1960&) described this species under the name G. acutispira from the G. 

 pseudomenardii - G. velascoensis Zones of the Paderno d'Adda section of northern 

 Italy which were regarded by them as Montian-Thanetian. 



Hillebrandt (1962) recorded this species to range throughout his Lower, Middle 

 and Upper Paleocene of Austria, which he regarded as Montian, Landenian and 

 Ilerdian respectively, although his forms appear to be different from Loeblich & 

 Tappan's original description and figures. 



In the Esna-Idfu region G. occlusa appears in the Upper Paleocene G. velascoensis 

 Zone. It floods the basal part of this zone, the G. pseudomenardii Subzone and fades 



