280 FORAMINIFERA 



ventral side completely so; chambers large and inflated; wall 

 calcareous, perforate, with a clear lunate space of small size 

 on the chamber above the aperture ; aperture broadly oval on 

 the ventral side of the last-formed chamber, without a lip. 

 Miocene to Recent. 



Genus NEOCRIBRELLA Cushman, 1928 



Plate 54, figures 10, 11 



Genoholotype, Discorbina globigerinoides Parker and Jones 

 Neocribrella Cushman, Contr. Cushman Lab. Foram. Res., vol. 4, 1928, 



p. G. 

 Discorbina (part) Parker and Jones, Phil. Trans., vol. 155, 18G5, pp. 



385, 421. 



Test trochoid but becoming somewhat involute in the later 

 stages ; chambers comparatively few, inflated ; wall calcareous, 

 perforate; aperture in the adult composed of several small 

 rounded pores in a slight depression of the ventral face of the 

 chamber. 



Eocene. France. 



As restricted here, the Rotaliidae includes those calcareous 

 perforate forms which are trochoid, with definite dorsal and 

 ventral sides and the aperture wholly ventral. The genera make 

 a natural grouping closely related to one another and the steps 

 between the genera often well filled by the simpler or more 

 complex species. The family may be derived through the conical 

 forms of Spirillina and the simple and more primitive forms of 

 PateUina and Discorbis. The more primitive genera have the 

 umbilicus open, but this is filled in the higher forms. The earlier 

 genera have simple walls, the higher ones as in Rotalia with 

 double walls and a secondary canal system. There is a gradual 

 progression from very simple structures to those foreshadowing 

 the specialized families which are derived from the Rotaliidae. 



FAMILY 34. AMPHISTEGINIDAE 



Test trochoid, all chambers visible from the dorsal side except 

 in involute forms of A^nphistegina, those of the last-formed 

 whorl only visible on the ventral side, the ventral side with 

 angular supplementary chambers coming in between the regular 

 series, roughly rhomboid in shape as seen from the surface; 



