90 BULLETIN 104, UNITED STATES NATIONAL MUSEUM 



make clear the fact that the Globigerinidae have developed from the 

 Rotaliidae as a specialized group adapting themselves to a pelagic 

 condition. In Cycloloculina, there is developed the annular form 

 which in its apertural characters allies it more or less closely to 

 Orbulina, and by its spinose condition to the others of the Globoro- 

 taliidae. Sherbornina is apparently close to Cycloloculina. 



KEY TO THE GENERA 



I. Test trochoid throughout. 



A. Periphery truncate, usually with a double keel Globotruncana 



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 



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



p. 91; Special Publ. No. 1, Cushman Lab. Foram. Res., 1928, p. 311. 

 Rosalina (part) of Authors. 

 Discorbina (part) of Authors. 

 Globigerina (part) of Authors. 

 Rotalia (part) of Authors. 

 Pulvinulina (part) of Authors. 



Genoholotype. — Pulvinulina area Cushman. 



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 umbi- 

 lical area; apparently pelagic in part. 



Upper Cretaceous to Recent. 



GLOBOTRUNCANA UNNAEANA (d'Orbigny) 



Rosalina linnaeana d'Orbigny, in De la Sagra, Hist. Fis. Pol. Nat. Cuba, 

 1839, "Foraminiferes," p. 101, pi. 5, figs. 10-12. 



This species is described as excessively rare in shore sands of Cuba. 

 No similar specimens have occurred in all my shallow water collec- 

 tions from the West Indies nor have specimens been found in any of 

 the many Albatross dredgings from this same region. Its resemblance 

 to the Upper Cretaceous species of this genus leads one to the con- 

 clusion that it may have been derived from Cretaceous sediments. 



Some of the specimens now found living in the Indo-Pacific may 

 possibly belong in this genus, but there seems to be no living repre- 

 sentative in the western Pacific. 



