180 THE FOEAMINIFEEA 



CHAPTER XII 

 THE FAMILY CHEILOSTOMELLID.E 



Only four genera are at present included in this 

 family — namely, EUipsoidina, Cheilostomella, Sea- 

 broohia, and Allomorpliina. 



The test is always calcareous, usually thin, and 

 finely perforate. The segments, of which there are 

 always more than one, are arranged either succes- 

 sively along an axis, placed alternately to one another 

 at either end of the test, or grouped in cycles of three. 

 The chambers are always more or less embracing. 

 The aperture is either a curved or straight slit at the 

 end or margin of the last segment. 



Possibly the best known genus of this family is 

 CJieilostoniella, in which the chambers are placed 

 alternately at either end of the long axis of the test. 

 The separate segments are inflated, and the shell- 

 w'alls of the chambers almost entirely conceal one 

 another by their embracing growth. 



In EUipsoidina the chambers are entirely embrac- 

 ing, and a solid shelly column runs from the top of 

 one chamber to the top of the succeeding one. 



Allomorpliina resembles Clieilostomella in the 

 alternation of the position of the chambers, but the 

 arrangement is in a cycle of three. 



