75 



CHAPTEE YIII 



THE FAMILY MILIOLID^ 



This very important division comprises the whole of 

 the porcellanous-shelled Foraminifera, and the tests 

 are further distinguished by their imperforate shell- 

 wall (sub-order Ijuperfoi-afa vel PorceUanea, Rupert 

 Jones). 



They are divided by H. B. Brady into six sub- 

 families, more or less closel}' related to one another. 



The characteristic features of the foraminiferal 

 shell in the family Miliolid.e are as follows : — 



' Test imperforate ; normally calcareous and por- 

 cellaneous, sometimes encrusted with sand ; under 

 starved conditions {ejj. in brackish water) becoming 

 chitinous or chitino-arenaceous ; at abyssal depths 

 occasionally consisting of a thin, homogeneous, 

 imperforate, siliceous film ' (H. B. Brady). 



The shell wall of the miliolids is in nearly all 

 cases of a smooth texture and usually chalk-white in 

 appearance. In some examples, how^ever, the surface 

 is pitted, reticulated, or furrowed, whilst others have 

 their surfaces encrusted with sand grains or shelly 

 particles. Young specimens are, as a rule, trans- 

 lucent and opalescent. This latter appearance is a 

 marked character with the group, for on mounting a 



