14 FORAMINIFERA 



chambers, Fig. 1. The suture ordinarily is the line of that por- 

 tion of the wall between two adjacent chambers of the same 

 whorl and inside the test may consist of the old enclosed wall of 

 the chamber as seen in section. In many of the higher forms a 

 complete wall is built with each chamber, that is, the new cham- 

 ber builds a floor over the included portion of the preceding 

 chamber. This results in a double wall in sections. Between 

 these two walls there is developed in the Camerinidae for exam- 

 ple a series of tubules which may be complex and lead to all parts 

 of the interior of the test comparable in general appearance to a 

 circulatory system in the higher animals. 



Sutures may be flush with the surface, more commonly de- 

 pressed, or in some cases raised above the general surface. They 

 are often very much thickened and are then spoken of as "lim- 

 bate", a character of importance in descriptive work. 



Wall. The materials of which the wall of the test are made 

 have already been discussed. In most foraminifera the wall is 

 perforate. These openings either large or small allow the fine 

 protoplasmic materials access to the exterior as well as through 

 the larger aperture. Occasionally the perforations may be very 

 definitely placed as in the higher forms such as the Globiger- 

 inidae (PI. 47, figs. 16, 17) where each is in a polygonal area of 

 the surface. 



The wall may be locally thickened giving rise to a pattern as 

 is seen in some species of Lagena, in Epistomina (PI. 40, fig. 

 6 5) and elsewhere. The thickening gives whiter areas against 

 a darker background of the thinner portions. In the Globiger- 

 inidae a much specialized character is found in the develop- 

 ment of fine spines clothing the test. These are outgrowths of 

 the wall and in these specialized pelagic forms may have a func- 

 tion in supporting the protoplasm which often becomes attenu- 

 ated and many times the diameter of the test. 



In some of the higher groups especially the orbitoids there 

 are solid masses called "pillars" developed in the wall. These 

 may start very early and be continued to the surface throughout 

 further development. The presence or absence of these is of 

 diagnostic importance in several groups. 



Ornamentation. The calcareous foraminifera especially are 

 often highly ornamented. This seems to be due in many cases 

 to an excessive amount of calcareous material. The ornamenta- 



