152 
XII. Fig. 8, is an interesting fossil ; terminating, at the lower end, in a 
point, from which the pedicle proceeded, and having in its superior part, 
the opening into its larger cavity, and on its sides the numerous openings, 
in which its peculiar hydrae had their residence. 
I must once more observe, before I quit the fossils of this family, 
that I have, in several instances, classed as alcyonia, bodies, which 
appear, in some respects, rather to accord with the genus doris, ascidia, 
or actinia; but which, in their general characters, differ so widely 
from any of these bodies with which we are at present acquainted, as 
to prevent their being placed under any existing genus. Here, 
perhaps, they had better remain, until more illustrative specimens 
shew their real nature, and the genus to which they more properly be- 
long. 
LETTER XVI. 
ENCRINITES AND PENTACRINITES TROCHITES HISTORY OF 
VARIOUS SPECIES DESCRIBED ORIGINAL ANIMAL MEMBRANE 
DEMONSTRATED, ...SCREW-STONE. 
Wb shall now proceed to the examination of a series of animals, 
which, whether we consider their extraordinary forms, the immense 
numbers in which they must have existed, in a living state, in the for- 
mer world ; or their being now, except in a solitary instance or two, 
to be traced only by their petrified remains, under the surface of the 
earth, or on the summits of mountains, undoubtedly offer to us as 
rich a field of observation as the most arduous inquirer could wish to 
explore. 
