THE TEST 15 



tion may involve various parts of the test in varying degrees, 

 such as the general surface of the chamber, the sutures, the 

 periphery, the spiral suture, or the aperture. 



Patterns in the chamber wall due to difference in thickness 

 have already been noted. There may also be pits either irregu- 

 larly distributed or making up more or less geometrical patterns 

 in the wall. These depressions in the higher forms like the 

 Globigerinidae (PI. 47, fig. 2), the Rupertiidae, etc., may produce 

 a definite cancellated appearance of the wall due to the greater 

 thickening along the sides of polygonal areas with the perfora- 

 tions in the center. 



The most common ornamentation of the general chamber wall 

 is in the form of raised areas. These may take the form of 

 raised costae, knobs, spines, or various types of raised mesh- 

 work. These raised forms of ornamentation may be generally 

 scattered, form characteristic patterns, or be confined to certain 

 definite portions of the chamber surface. 



The sutures may be raised into definite ridges or costae (PI. 

 40, fig. 1 a) , and these costae may again be broken up into rows 

 of bead-like knobs (PL 40, fig. 10 a) or may even develop spines. 

 The sutures are often thick and limbate, or clear shell material 

 appearing darker against the lighter areas between the sutures 

 (PI. 40, fig. 6). Where the sutures meet the periphery, spines 

 are often developed or peripheral keels connecting with the 

 sutures. 



The periphery of the test in spiral forms is a place where 

 ornamentation is often greatly developed. It may consist of a 

 thickened keel or one that is thin and becomes a broad carina 

 in several families (PI. 24, fig. 2). Spines either in relation to 

 the ends of the sutures, the keel or the general surface are often 

 developed to large size (PI. 35, figs. 1-5, 17). Costae of the gen- 

 eral surface may be developed into spines at their outer edge. 



The spiral suture is itself often thickened, standing above the 

 general surface or broken into knobs. Its ornamentation is 

 usually more closely related to that of the sutures and periphery 

 than to that of the general chamber surface. 



About the aperture, spinose or granular surfaces are often de- 

 veloped in several different families. Where a neck and lip are 

 developed there are often spines about the outer surface. In 

 forms like Buliminoides (PI. 35, fig. 11) or some species of Dis- 



