BROWN, RUGOSE CORALS 
63 
Figure 26 a is a section from the open calyx of the corallite. Here the 
septa are all short and about equal 
in length, and project freely into the 
cup. Small tertiary septa alternate 
with all the primary and second¬ 
ary septa. Figure 26 b is from the 
corallite just below the open cup. 
In it there are present the four pri¬ 
mary septa, four pairs of secondary 
septa in each cardinal quadrant and 
seven pairs of secondary septa in 
each counter quadrant. Small 
tertiary septa are present and alter¬ 
nate with all the primary and sec¬ 
ondary septa. Figures 26 c-g show 
other stages in the development 
already described. Figures 26 c, d 
and e show very well the irregular 
method of grouping or uniting of 
the inner edges of the secondary 
septa to form the peculiar pseudo¬ 
columella. Figure 25 shows similar stages from another individual. 
A study of the developmental stages of these individuals shows that 
throughout the counter quadrants are in advance of the cardinal quadrants, 
and this feature becomes more pronounced in the later stages of develop¬ 
ment. In the earliest stages obtained, one pair of secondary septa have 
appeared in the counter quadrants, and two pair appear in these quadrants 
before the first pair arise in the cardinal quadrants. Up till the time when 
the fourth and last pair of septa are developed in the cardinal quadrants, 
the number of septa in the counter quadrants is just one more than in the 
cardinal quadrants. After all the septa are developed in the cardinal 
quadrants, two more pairs appear in the counter quadrants, making seven 
pairs of secondary septa in the counter quadrants as compared with four 
pairs in the cardinal quadrants. Thus it is seen that the acceleration in 
development of the counter quadrants progressively increases in the life of 
the individual and is very strongly marked in the later stages. (Compare 
stages in Stereolasma rectum Hall from the Devonic.) 
