FAMILY 10. VERNEUILINIDAE 121 



Genus CRIBROGENERINA Schubert, 1907 



Plate 11, figure 24; plate 13, figure 8 

 Genoholotype, Bigenerina sumatrana Volz 



Cribrogenerina Schubert, Neues Jahrb. fiir Min, Beil. Bd. 25, 1907, 

 p. 245. 



Test typically uniserial throughout unless the earliest 

 chambers in the microspheric form are biserial; wall finely 

 arenaceous ; aperture in the early chambers simple, in later ones 

 cribrate, in a terminal plate. 



Carboniferous and Permian. 



This family is directly derived from a planispiral ancestry 

 such as the Lituolidae by the addition of the biserial character 

 resulting from an elongate spiral settling down to a turn of 180° 

 for each chamber. In the more primitive genera, the early 

 stages in the microspheric form show the planispirally coiled 

 stage, but this is lost in the higher ones. In a number of respects 

 the family apparently reached its climax in the Carboniferous 

 and Permian although further study may show these forms to 

 be possibly from a distinct ancestry. 



For a further discussion of this family and the two following 

 ones, see Cushman, Phylogenetic Studies of the For^minifera, 

 Part II, (Amer. Journ. Sci., vol. xiv, 1927, pp. 317-324). 



FAMILY 10. VERNEUILINIDAE 



Test, at least in the early stages, triserial, later biserial in 

 some genera and in most specialized ones becoming uniserial; 

 wall arenaceous, the amount of cement varying in different 

 genera and species; aperture simple or multiple. 



KEY TO THE GENERA 



T. Test triserial throughout. 



A. Generally rounded in section, aperture at the margin of the 



chamber Verneuilina. 



B. Sharply angled in section, aperture terminal Tritaxia. 



II. Early stages triserial, adult biserial. 



A. Aperture at or near the base of the chamber margin.. . .Gaudi'yina. 



B. Aperture terminal, with a neck Heterostomella. 



III. Early stages triserial, adult uniserial. 



A. Chambers simple Clavulina. 



B. Chambers labyrinthie or divided Tritaxilina. 



