302 FORAMINIFERA 



Test in the earliest stages generally planispiral, later chambers 

 irregularly embracing; wall calcareous, perforate; aperture in 

 the young, a crescent-shaped opening, in the adult, rounded, with 

 a flat, rounded, tooth-like projection. 



Cretaceous to Recent. 



The genera included in this family show a regular progression 

 from the more primitive AUomorphina, which is trochoid and 

 allied to the Rotaliidae, to the specialized Seabrookia. The plani- 

 spiral forms connect with the irregularly involute Sphaeroidina 

 which has a Pullenia-\ike young. Some of the genera on account 

 of the rounded form have been placed in the Globigerinidae but 

 they have no trace of the spinose or cancellated test, or the coarse 

 wall characteristic of the Globigerinidae. 



FAMILY 39. GLOBIGERINIDAE 



Test, at least in the early stages, trochoid, umbilicate; wall 

 calcareous, rather coarsely perforate, usually with a cancellated 

 surface, in well preserved specimens of the simpler genera with 

 fine spines; aperture typically large but in the higher genera 

 consisting of numerous small openings variously placed. 



KEY TO THE GENERA 



I. Test trochoid throughout. 



A. Not involute. 



1. Aperture single, ventral Globigerina. 



2. Apertures several. 



a. , Apertures small, all along the sutui'es Candeina. 



b. Apertures large, one umbilicate, others along the suture. 



Globigcrinoides. 



B. Involute. 



1. Aperture not in a deep depression Pulleniatina. 



2. Aperture in a deep depression Sphaeroidinella. 



II. Test not trochoid throughout. 



A. Test in the adult planispiral. 



1. Wall cancellated, spines fine and numerous GlobigerineUa. 



2. Wall rather smooth, spines coarse, flat, fevi^ Hastigerina. 



B. Test in the adult irregularly spiral, spines at the ends of the 



chambers Hastigerinella. 



C. Test in the adult with the last chamber spherical and completely 



enclosing the earlier ones Orbulina. 



