NO. 4 FORAMINIFERA CUSHMAN 35 



varying much in coarseness in the different species ; aperture variable 

 as in the various species of Textularia, either an opening at the base 

 of the inner margin of the chamber, between it and the wall of the 

 preceding chamber, or a perforation near the base of the inner margin, 

 often with a raised border, or in some species a terminal more or less 

 circular opening. 



Genus TRITAXILINA Cushman, 19 ii 



Plate 6, fig. 2 



Test in its early development triserial, later becoming biserial 

 and in the adult uniserial ; chambers numerous, distinct, interior 

 labyrinthic ; wall arenaceous ; aperture in the triserial portion elongate 

 with a valvular lip, at the edge of the inner side of the chamber, in 

 the adult central, terminal, usually with a series of peripheral teeth 

 projecting in and partially closing the opening. 



Genus CLAVULINA d'Orbigny, 1826 



Plate 7, fig. I 



Test free, elongate, cylindrical or angled ; early portion consisting 

 of a number of chambers arranged triserially ; later portion con- 

 sisting of numerous chambers arranged uniserially ; walls arenaceous, 

 usually smooth ; aperture in early chambers with a valvular tooth ; 

 in the later portion aperture central or nearly so, rounded, and with 

 or without a tooth. 



Genus MIMOSINA Millett, 1900 



Test triserial ; wall thin ; aperture of two openings, one a slit at the 

 base of the ventral face, the other varying in shape and near the 

 outer end of the ventral face ; the two sometimes connected on the 

 interior of the test. 



Subfamily 4. BULIMININAE 



Test elongate spiral ; wall usually hyaline at least in the early stages, 

 calcareous ; perforate ; aperture typically a comma-shaped slit. 



Genus BULIMINA d'Orbigny, 1826 



Plate 5, fig. 8 



Test usually fusiform or tapering, free, composed of numerous 

 chambers arranged typically in a spiral, each chamber situated above 

 the third preceding one, making a triserial arrangement, not always 



