DEVELOPMENT. OF PALEOZOIC CORALS 6 
nection with the first series. 
UL 
Their outer borders extend to the inner- 
most series of interseptal dissepiments and these dissepiments occupy 
the remainder of the interior to the outer wall. 
at irregular intervals, as parallel 
bars extending inward and up- 
ward in an arching manner. 
The essential characteristics, 
with the exception of the com- 
pleted inner wall, are more 
specialized in the species C. 
archiact from the Hamilton of 
Thunder Bay, Michigan. In a 
single corallum are found indi- 
viduals representing the several 
stages of development. Thus 
are found individuals, in the 
young stages of which the inner 
wall has not appeared, others in 
which it is open at the cardinal 
septum, and still others in which 
it is completely closed, which is a 
rarer feature in this species than 
in C. subcaes pitosum. When the 
inner wall is incomplete, the car- 
dinal septum often extends into 
the inner central area (Fig. 7). 
This peculiarity has not been 
observed in any other species 
containing a true inner wall. 
When the wall is completely 
closed in this species, the cardinal 
septum extends to the dissepti- 
The carinae appear, 
C, 
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Fic. 6.—Longitudinal section cf Cras 
pedophyllum subcaes pitosum showing 
the slight tapering of the corallite; and, 
from the margin toward the center: the 
interseptal dissepiment; the carinae; the 
second tabulate area; a section of the 
inner wall and the central tabulate area. 
mental bridge which spans the cardinal fossula, becoming identical 
with a secondary septum with tertiary septa separating it from the 
other secondary septa. 
Closely allied to C. archiaci from above locality, is Eridophvllum 
verneuilanum from Columbus, Ohio, the difference in internal structure 
