AGE OF CORAL REEFS. 197 
With regard to the geological position of the 
Actiniz we can say nothing, because, if their soft, 
gelatinous bodies have left any impressions in 
the rocks, none such have ever been found; but 
their absence is no proof that they did not exist, 
since it is exceedingly improbable that animals 
destitute of any hard parts could be preserved. 
The position of the Corals on a Reef accords 
with these series of structural gradation and ge- 
ological succession. It is true that we do not 
SUCCESSION ON THE REEF. 
Halcyonoids. 
CoraL Reer. \ Porites. 
Meeandrines. 
Astreeans. 
find the Actiniz in the Reef any more than in the 
crust of the earth, for the absence of hard parts in 
their bodies makes them quite unfit to serve as 
Reef-Builders. Neither do we find Fungida, for 
they, like all low forms, are single, and not con- 
fined to one level, having a wider range in depth 
