128 FORAMINIFERA 



Valvuliva (part) of authors. 

 Tritaxia (part) of authors. 



Test elongate, cylindrical or angled, early portion consisting 

 of chambers arranged triserially, in most species quickly fol- 

 lowed by a uniserial series, but in some primitive species with a 

 biserial stage between; wall arenaceous; aperture, in the early 

 stages, a simple opening at or near the inner margin, later be- 

 coming terminal, often with a neck, in some species with an 

 apertural tooth. 



Cretaceous to Recent. 



This family is very closely related to and derived from the 

 biserial Textulariidae. The triserial character is shoved back 

 by acceleration, and is replaced by biserial and uniserial stages 

 in the higher genera. The family apparently reached its climax 

 in the Cretaceous. 



FAMILY 11. VALVULINIDAE 



Test in the early stages triserial, later with a secondary spiral 

 development, finally in some genera becoming annular; 

 chambers simple or in the higher forms labyrinthic; aperture 

 simple or cribrate. 



KEY TO THE GENERA 



I. Test coiled throughout. 



A. Triserial thi'oughout Vahmlina. 



B. Early stage triserial, later several chambers in a whorl. 



1. Aperture simple. 



a. Aperture at the margin of the chamber.. . . Arenohulimina. 



b. Aperture extending into or included in the face. 



A taxophrag')niuni. 



2. Aiierture cribrate Crihrohulimina. 



C. Later chambers annular, test conical. 



1. Test elongate, early stages prominent Lituonella. 



2. Test broad, early stages inconspicuous Coskinolina. 



Genus VALVULINA d'Orbigny, 1826 



Plate 12, figure 16; plate 13, figure 20 



Genotype, by designation, Valvulina triangularis d'Orbigny 



Valvulina d'Orbigny, Ann. Sci. Nat., vol. 7, 1826, p. 270. 



Rotalina (part) Williamson, Rec. Foram. Great Britain, 1858, p. 55. 



Test triserial, conical, umbilicate, usually attached; wall 



