DEVELOPMENT OF PALEOZOIC CORALS 63 
alar pseudo-fossulae, and all the septa have assumed their complete 
radial direction with the exception of one on either side of the cardinal 
fossula. 
The opening in the inner wall in the region of the cardinal fossula 
is very persistent and remains permanently in normal individuals of 
the species, constituting the character of the horseshoe shaped inner 
wall of Craspedophyllum (Fig. 4.) In normal types it persists 
into the adult, but in the last stages of accelerated types it is closed. 
While this opening remains, the two septa on either side of the car- 
dinal septum remain pinnate and form the ends of the incomplete 
wall (Fig. 3). The septa very slowly arrange themsvlves radially 
and in a similar manner to the 
earlier ones contribute their por- 
tion to the ends of the inner wall 
(compare Figs. 3 and 4). ‘The 
septa on either side of the car- 
dinal septum are now more 
radially arranged than in Fig. 3, 
and the connection between the 
inner central areaand the cardinal 
fossula is more constricted. It is 
seen in Fig. 4 that as these two 
septa become radially directed, 
the neck connecting the cardinal 
fossula with the inner central Fic. 4.——Cross-section of the same 
area is gradually constricted until corallite taken 5mm higher up than 
: : Fig. 3. Diameter 4™™. a. The alar 
a stage 1s reached, as shown in septa. A slight irregularity of growth 
Fig. 5, when this neck is spanned on the left. 
by a similar dissepimental bridge 
which early in the life of the individual cut off the connection 
between the alar pseudo-fossulae and the inner central area. It is 
evident that in further development of the individual, the cardinal 
fossula cannot be distinguished and to all appearance becomes 
similar to one of the interseptal spaces. The septa on either side 
of the cardinal septum have now assumed a nearly radial direction 
and the dissepimental bridge spans the cardinal fossula making 
the inner wall complete. In Fig. 5 one can clearly trace the 
