FAMILY 9. TEXTULARIIDAE 113 



FAMILY 9. TEXTULARIIDAE 



Test in the earliest stages, at least in primitive forms, plan- 

 ispiral, later in all but the most accelerated forms developing a 

 biserial stage, final development taking various forms, usually 

 becoming uniserial in the more specialized types; wall 

 arenaceous, with a varying proportion of cement in different 

 genera and species; aperture typically at the inner margin of the 

 last-formed chamber in the biserial forms, becoming terminal 

 and sometimes multiple in the uniserial forms. 



KEY TO THE GENERA 



I. A large portion of the early test planispiral, later biserial. 



Spiroplectammina. 



II. Test mostly biserial, no uniserial stage. 



A. Attached Textularioides. 



B. Free. 



1. Aperture simple. 



a. Chambers not labyrinthic Textularia. 



h. Chambers labyrinthic Textulariella. 



2. Aperture multiple. 



a. Apertures in a row at the inner margin, test strongly 



compressed Cuncnlina. 



b. Apertures in the terminal face Cribrostomiim. 



III. Test with both biserial and uniserial stages. 



A. Aperture simple. 



1. Test not compressed, aperture circular Bigenerina. 



2. Test much compressed, aperture elongate Vulvulina. 



B. Aperture multiple, terminal Climacammina. 



IV. Test wholly uniserial. 



A. Aperture simple, 



1. Test not compressed. 



a. Not distinctly perforate Monogenerina. 



h. Coarsely perforate Nodosaroum. 



2. Test compressed. 



a. Bilaterally symmetrical in sections, both sides concave. 



Geinitzina. 

 h. Unequally compressed, one side convex, one concave. 



Lunucammina. 



B. Aperture multiple, terminal. ' Cribrogenerina. 



