94 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



with accessory apertures, only poorly preserved ; wall calcareous, perforate, 

 except for the imperforate keels, peripheral band and tegilla ; surface generally 

 smooth but with a few scattered papillae on the dorsal side especially in the early part. 



Dimensions of described specimen. 



Maximum diameter = 0-52 mm. 



Minimum diameter = 0-49 mm. 



Thickness = 0-40 mm. 



Main variation. 



1. Chambers 14-21, arranged in 3-4 whorls, which are generally dextrally coiled 



(all the specimens studied coiled dextrally). 



2. Chambers in the last whorl 4-5, most commonly 4, slightly to moderately 



undulate and slowly to moderately increasing in size ; the last chamber is 

 sometimes slightly smaller than the penultimate. 



Remarks. Globotruncana contusa patelliformis is distinguished from G. contusa 

 contusa by its more regular, far less plicated, subconical test ; its narrow elongate, 

 fornicata-type chambers on the ventral side ; strongly curved forward, raised and 

 beaded ventral sutures and distinctly elongate early chambers. It is also distinguish- 

 ed from the other members of the G. contusa group by the shape of its ventral cham- 

 bers and sutures and its robust, regular test. 



Globotruncana contusa patelliformis is believed to have evolved from G. fornicata 

 fornicata Plummer through G. adamsi sp. nov., as suggested by their morphological 

 characters and stratigraphical distribution. The early part of G. contusa patelli- 

 formis closely resembles G. adamsi, and the ventral side of the two forms is also very 

 similar. However, Gandolfi (1955) suggested the evolution of G. contusa patelli- 

 formis from G. contusa scutilla which can be considered a very small G. contusa 

 patelliformis, but no transitional stages between these two subspecies were recorded 

 in the present study. Gandolfi also suggested that G. contusa patelliformis had 

 evolved into G. contusa contusa (Cushman) by the development of the sharply cut 

 polygonal periphery, plicated dorsal side, and depressed ventral sutures. 



Specimens of G. contusa patelliformis Gandolfi, from the Esna-Idfu region, con- 

 form well with the original description and figures of the holotype, and with topo- 

 types kindly forwarded to the present author by Dr. R. Gandolfi. 



Hypotype. P. 45522. 



Horizon and locality. Figured specimen from sample No. 18, W. El-Sharawna 

 section. 



Stratigraphical range. Gandolfi (1955) described G. contusa patelliformis 

 from the Colon shale of northeastern Colombia, and gave its range as Campanian- 

 Maestri chtian. However, analysis of the planktonic Foraminifera of the Colon 

 shale, described by Gandolfi, suggests a Maestrichtian age for the whole formation. 



Corminboeuf (1961) recorded the present subspecies from the Maestrichtian of 

 Switzerland. 



