DEVELOPMENT OF PALEOZOIC CORALS 61 
as revealed in successive sections of a single corallite. It is seen that 
each alar region is that at which new septa are successively added to 
the primary septa (Fig. 1). 
The addition of new septa takes place in such a manner that the 
new short septa are inclined toward the older, with which they are 
permanently fused with their inner borders, never being detached 
even in the most developed stages. It is to this persistent fusion of 
the inner borders of the long septa that the inner wall is directly due, 
as will be explained presently. It is evident that the addition of new 
septa is the same as Duerden has found to be true in the genus 
Streptelasma (Biological Bulletin, Vol. IX, No. 1, p. 30), but that 
genus differs from Craspedophyllum in that the septa become free 
toward the close of development. It differs from the genus Hadrophyl- 
lum, as in the latter the alar pseudofossulae’ and the pinnate arrange- 
ment of the septa are maintained in the most developed stages, whereas 
in Craspedophyllum the alar pseudo-fossulae become obliterated 
very early in the life of the individual by the formation of a dissepi- 
mental bridge, and the pinnate arrangement of the septa, with the 
exception of one or two septa on either side of the cardinal fossula, 
gives place to the more specialized 
radial arrangement. 
The growth of septa in the early 
stages is very rapid, but the central 
-area is always left intact never being 
invaded by them. This gives the 
septa an irregular appearance which 
greatly adds to the difficulty of detect- 
ing the Streptelasma mode of arrange- 
ment; the difficulty being further 
‘augmented by the tendency of the 
septa to arrange themselves radially Fic. 2.—Section of same coral- 
andeyvet to) nemaimvattached withthe  lcyo0 ) seh UP. Diameter 
9 : ; 3mm, a. The alar septa.- The 
innem borders: aplt_issevidentsthat ior a. ap pcay. con iecicg oath 
the septa to remain attached in this the inner central area. 
-manner, only the peripheral portion can 
become radial at first, but this portion gradually extends inward until 
t Grabau and Shimer, North-American Index Fossils, p. 48. 
