36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ']'] 



visible from the surface except in the last convolution ; wall cal- 

 careous, perforate, usually thin and transparent, but thickening some- 

 what with age, smooth or ornamented with raised costse, spines, 

 etc. ; aperture typically a comma-shaped slit broadest above and 

 tapering obliquely to a point below, usually with a raised margin and 

 often partly closed by a tooth-like rim at one side. 



Genus BULIMINELLA Cushman, 191 1 

 Plate 6, fig. 3 



Test composed of chambers triserially arranged, but in later 

 development becoming involute and spirally coiled, the aperture being 

 in the umbilicus thus formed; wall calcareous, perforate; aperture in 

 the species but little twisted spirally, long and narrow, nearly vertical, 

 in the closely spiral species becoming rounded in the middle of the 

 concave umbilical area. 



Genus BULIMINOIDES Cushman, 191 1 



Plate 7, fig. 2 



Test triserial, spiral, elongate, subcylindrical ; wall calcareous, per- 

 forate; aperture nearly circular, terminal, in a depression of the 

 truncated apertural end. 



Genus VIRGULINA d'Orbigny, 1826 

 Plate 6, fig. 4 



Test elongate, tapering, typically biserial, often becoming irregularly 

 twisted in a spiral manner ; chambers distinct ; sutures usually de- 

 pressed ; wall calcareous, thin and translucent, in adults sometimes 

 becoming thicker and opaque, perforate ; aperture typically a comma- 

 shaped opening with the narrow end coming to the base of the 

 chamber ; color white. 



Subfamily 5. CASSIDULININAE 



Test both spiral and biserial, the early chambers somewhat spirally 

 placed, the later ones biserial ; wall usually hyaline and perforate ; 

 aperture comma-shaped. 



Genus CASSIDULINA d'Orbigny, 1826 



Plate 6, fig. 5 



Test complex, at least the early portion coiled, the chambers 

 arranged biserially, alternating on the sides of the axis of coiling, 



