228 FORAMINIFERA 



Test globular, composed of generally concentric chambers 

 divided into irregular chamberlets, generally flattened and 

 parallel to the surface in concentric layers, communicating with 

 adjacent chambers both in the same layers and in the layers 

 above and below; wall imperforate; apertures rounded, all at 

 the margins of the chamberlets. 



Recent. 



In this same group has been placed Bradya Stache, later 

 called Keramosphaerina Stache. These are Cretaceous forms, 

 and by some authors have been held not to be foraminifera. 

 Parkeria has also been placed with these same forms. For a 

 detailed discussion of the evidence, the reader is referred to 

 Silvestri, Sulla "Bradya tergestina" Stache (Riv. Ital. Pal., Ann. 

 30, 1924, pp. 17-26, 1 plate). 



FAMILY 29. HETEROHELICIDAE 



Test in the more primitive forms planispiral in the young, 

 later becoming biserial, in the more specialized genera the 

 spiral and biserial stages reduced or wanting and the relation- 

 ships shown only by other characters ; wall calcareous, perforate, 

 ornamentation in specialized genera bilaterally symmetrical; 

 aperture when simple, usually large for the size of the test, 

 without teeth, in some forms with an apertural neck and 

 phialine lip. 



KEY TO THE GENERA 



I. Coiled stage in the young prominent. 



A. Biserial chambers few, increasing in size as added Heterohelix. 



B. Biserial chambers many, of nearly uniform size. 



1. No uniserial chambers developed Spirojylectoides. 



2. Uniserial chambers developed in the adult. . . . Sinroplectinata. 



II. Biserial stage in the young prominent. 

 A. Biserial throughout. 



1. Chambers more or less globular Gumbelina. 



2. Chambers compressed. 



a. Periphery much thickened Bolivinoides. 



b. Periphery concave and with sharp keels Bolivinita. 



c. Periphery sharp, chambers elongate,, Bolivinella. 



