416 Mr. H. J . Carter on Calcareous Hexactinellid 
and there, passing obliquely through this fine layer, may be 
seen Moseley’s superficial branches of this system. 
I omitted to state in my last paper that although this system 
is only seen here and there on the surface of Millepora alci- 
cornis, it comes into view directly the surface is slightly taken 
off with a very sharp knife; but it should be remembered that 
it is so thin that, as in Stromatopora, the least abstraction of 
the surface may bring it into view or remove it altogether, as 
the case may be. 
Returning to the surface of these fossils, we find no. 1 possess- 
ing a hole laterally about1-8th of an inch in diameter, narrowing 
inwards to near the centre, and issuing from it a number of 
grooves which spread over half the surface in a branched 
venation ; while the other part, which is more or less dimpled 
like Parkeria, presents, every here and there, a stellate ar- 
rangement of such grooves issuing from the dimple. 
Following this up we seem to find its homologue in the 
excavation at the ends of nos. 2 and 3, from which also pro- 
ceeds the same kind of branched sinuous venation. Of the 
nature and function of the soft parts which occupied the hole 
and its grooved venation I cannot offer an opinion, further 
than that it might have been of the same nature and for the 
same purpose as that of the “ horizontal canal-system,” viz. 
for the formation of additional layers upon the test or corallum. 
The question may also be suggested here, whether the hole seen 
in many, perhaps most, specimens of Millepora globularis is 
not of the same kind (‘ Annals,’ 1878, vol. 1. p. 307). 
Lastly, I must state here again that, as there are so many 
forms of the fossils figured by Goldfuss &c. under one head 
that belong to totally different organisms, many, indeed, to 
real sponges, as shown by Prof. Zittel (‘ Annals,’ 1. ¢.), it is 
very desirable, as I have before stated, that they should be all 
‘“‘yelegated to their proper position in the animal kingdom” 
by the paleontologist. All I can do is to point out, as Prof. 
Zittel has done for sponges, the structure of those which have 
accidentally come before me that may be termed Hydractinian 
or Hydrozoic. 
One cannot help seeing here, too, that while the Hydrozoa 
(as Stromatopora) played such a great part in the formation of 
the Devonian-Limestone reef, they were also very plentiful 
under other forms during the Cretaceous period, and that (in 
Millepora alcicornis &c) they are doing the same kind of 
work in the formation of coral reefs at the present day. 
With reference to the replacement of silex by calcite I have 
just been examining a large fossil sponge from the Chalk more 
or less chalcedonized (in size 7 x 5x 23 inches, shaped like 
