64 G. E. ANDERSON 
order of development of the septa by their inner borders retaining 
a slight indication of the pinnate arrangement in the early stages. 
Further development of the corallite will tend to make the septa per- 
fectly radial in direction and the inner wall, to which the primary and 
secondary septa are still firmly fused, assume a circular outline which 
is better illustrated in more specialized individuals than is shown in 
Fig. 5. At such a stage the true relation which exists between the 
inner wall and the long septa is not so evident. The former now 
develops quite independently of the septa, the inner borders of which 
may be considered as fused with the inner wall itself. The inner 
wall becomes circular at this 
stage, and it is evident that the 
cardinal fossula is no longer 
prominent. The cardinal septum 
has been reduced in size so as to 
be equal in length to a tertiary 
septum. 
The tertiary septa do not 
appear until the secondary septa 
are well developed (Fig.-1. shows 
no tertiary septa). These differ 
from the primary or secondary 
septa in being radially arranged 
Fic. 5.—Cross-section of same corallite from their first appearance in the 
taken 2™™ above section of Fig. 4. a. The outer wall, and consequently their 
inner borders are free and can, 
therefore, easily be distinguished 
from the secondary septa. They extend one-half the distance to the 
inner wall before the latter is closed in the region of the cardinal 
septum, and this constitutes their full growth. 
So far only the transverse sections at different stages have been 
discussed, though the longitudinal section (Fig. 6) is equally interest- 
ing. The central area is occupied by a series of tabulae the outer 
alar septa. c. The cardinal septum. 
Diameter 5™™. 
borders of which are fused in the inner wall, which is circumscribed 
by a second series of tabulae distinguished from the first series in 
being more delicate and more crowded. ‘The second series of tabulae 
are fused with their inner borders in the inner wall, but have no con- 
