FAMILY 40. GLOBOROTALIIDAE 311 



Discorhis. In many respects the Globigerinidae represent one 

 of the highest and most specialized families in the whole group 

 of the foraminifera. 



FAMILY 40. GLOBOROTALIIDAE 



Test in the early stages trochoid, the chambers with a rough, 

 cancellated exterior and often spinose, in the adult resuming 

 the ancestral rotalid form or becoming annular, but often re- 

 taining the rough, spinose surface; aperture typically opening 

 into the umbilical area, the older species often retaining the 

 protecting covering above the umbilical area, and traces of it 

 appear in the living forms; largely pelagic. 



KEY TO THE GENERA 



I. Test trochoid throug-hout. 



A. Periphery truncate, usually with a double keel Glohotruncayia. 



B. Periphery acute or rounded, with a single keel Globorotalia. 



II. Test becoming- annular. 



A. A single layer of chambers Cycloloculina. 



B. Chamberlets on the flattened surface Sherbornina. 



Genus GLOBOTRUNCANA Cushman, 1927 

 Plate 48, figure 11; plate 49, figures 1, 2 

 Genoholotype, PulvbmUna area Cushman 



Globotnmcava Cushman, Contr. Cushman Lab. Foram. Res., vol. 3, 1927, 

 p. 91. 



Rosalina (part) of authors. 



Discorbina (part) of authors. 



Globigerina (part) of authors. 



Rot alia (part) of authors. 



Pidvinulina (part) of authors. 



Test trochoid in the young the chambers usually globose, rough 

 and cancellated, the adult usually much compressed, the dorsal 

 and ventral sides either flat or convex, ventral side sometimes 

 slightly concave, the periphery truncate, usually with a double 

 keel on the dorsal and ventral sides; aperture on the ventral 

 side, often in well preserved specimens with a thin plate-like 

 structure over the umbilical area; apparently pelagic in part. 



Upper Cretaceous to Recent. 



