Cl » te riu is — 14 •* 
skeleton had been etched away; and, if so, there is a possibility 
of these apertures being secondary and accidental, and this alone 
would rule the specimen out of this genus. It is also character- 
istic of the Poritidae that the bases of the cal.icles fill up 
with tissue so as to be only occasionally traceable through the 
corallurru Here they are long open tubes. Then, again, it is 
very rare to see the tertiary septa end freely, and, as a rule, 
it is not like f on i. opera, to have such rigid septa. There is a 
fluency in the skeleton of this genus, with hardly a single ex- 
ception, which is in great contrast to the skeletal rigidity 
shown in this fossil; such subtle indefinable distinctions are 
often excellent guides e But even in the face of these difficulties 
we have to be true to our morphological analysis; and from this 
point of view I think that, on the whole, the balance of the 
direct structural evidence is in favor of its being a Gonlopora : 
the thin zigzag membranous walls, occasionally forming a reticulum, 
the large columella, the 24 septa, are all so much positive evi- 
