93 
spongy part of alcyonia, whilst the intervening spaces appeared to be 
tilled by a softer substance, a carbonate of lime. The substance was 
therefore partly immersed in dilute muriatic acid, by which the cal- 
careous part was speedily removed, with effervescence, and the sili- 
cious part left, possessing the fine fetiform texture of the spongy alcy- 
onium, surrounding the central opening already mentioned, as may 
be seen in the upper part of the figure. 
The fossil represented Plate VII. Fig. 9, approaches the nearest, in 
its general form and appearance, to the alcyonium cydonium Linnsei, 
the alcyonium primum of Dioscorides, or rather to the representation of 
this animal as given by Donati. It must, however, be, I believe, con- 
sidered as differing from any known animal of this genus. 
This fossil is of a roundish form, rendered unequal by shallow de- 
pressions about the width of a finger, which pass from the superior to 
the inferior part of the fossil, and are separated from each other by 
tuberculated ridges. At the upper part has been a circular opening 
more than half an inch in diameter ; and, at the lower part, is a rugged 
spot as though the pedicle had been here separated: a circumstance 
indeed which renders its affinity to the alcyonium described by Donati 
rather more doubtful. The substance of this fossil appears to be lime- 
stone which, probably from some tinge of iron, has obtained a reddish 
brown colour. It is not of a very close texture, apparently from the 
superadded calcareous matter not having accurately filled all the in- 
terstices between the fibres. Hence numerous small openings are, 
even in its present state, observable on its surface, which on close in- 
spection are seen to be such as would result from a loose or spongy 
texture. 
Whilst treating of the alcyonium, of the species to which this seems 
to approach, Donati particularly describes and delineates the curiously 
formed spiculae which constitute a part of its substance. The body, 
as well as the cortical part, he remarks, is formed of two substances ; 
