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sensation, as if its surface were beset with innumerable minute asperities, 
a sensation which I had been accustomed to feel, whilst handling such 
petrified alcyonia as had not suffered from attrition, and which ap- 
peared not to have been deprived of their cortical part. I am there- 
fore led to believe that, on this fossil, a considerable portion of the 
original cortical part still remains; but which has been entirely re- 
moved from those which have been just described. I am also induced to 
suppose, from the appearance of this fossil, that the surrounding rami- 
fying filaments were disposed between the cortical part and the body 
of the alcyonium ; and that, besides the office just attributed to them, 
they also served to connect the cortical investing part with the included 
spongy mass. 
The fossil, figured Plate IX. Fig. 7, appears to have been of the 
same species, and is, in many respects, exceedingly interesting. It 
has been imbued with silicious matter so transparent, that its highly 
polished transverse section displays the internal structure of the alcy- 
onium as plainly as it could have been discovered in the recent animal 
itself. The greater part had evidently been of a spongy texture ; the 
spongy substance itself being most distinctly visible with a lens of a mo- 
derate power. Through this substance, several interrupted lines, as the 
figure will shew, pass in regularly disposed radii from the centre to the 
circumference, and an examination of these with the magnifying lens, 
gives every reason to suppose that they are distinct from each other, 
and are transverse sections of those fibres which, passing from one part 
of the body to the other, have, by supporting it, served to preserve its 
form. They also have probably been fasciculi of muscular fibres, and 
may have served, in the living animal, to have produced that alternate 
contraction and dilatation of the external openings of this animal, 
which we have already spoken of, and which Marsilli has observed to 
take place in the external openings of sponges, when filled with the 
water on being taken out of the sea. Another observation of this 
same ingenious naturalist also leads to the supposition, that this con- 
