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dered them as alcyonia, he was by no means convinced, that they 
should be considered as species of that genus, or true alcyonia. 
The real petrifactions, Mr. Walch describes, as being chiefly the rete- 
porites, or fossil flustra ; the casts were chiefly of the astroites : and the 
impressions of the tubulites and fungites. Of the latter he believed 
but very little of the original substance remained on the Maestricht 
fossils ; he having never succeeded in any of his examinations, which 
he says were many, in discovering any of the fibrous texture, or of the 
lamellated part of these bodies ; but, on the contrary, he very fre- 
quently found that these bodies were formed entirely of the same 
substance as the matrix itself, and manifested not the least trace of 
any extraneous matter. It must, however, be here remarked, that 
Mr. Hoffman, agreeable to the candid acknowledgment of Mr. Walch, 
did really find, among a great number, two in which he could per- 
ceive the opening (oscula) proper to these animals. Still, however, 
Mr. Walch supposes that these fossils, which have acquired their 
figures from these bodies, have been formed by the filling up of their 
cavities with earthy matter. 
The opinions of Mons. Faujas St. Fond, respecting the origin and 
the formation of these fossils, correspond very nearly with those of 
Mr. Walch, excepting that he considers several of these fossils as 
formed of the changed animal matter, which Mr. Walch supposed 
to be casts of earthy matter, deposited in the cavities of the original 
bodies. 
I shall now proceed to the unpromising task of inquiring into the 
original nature of some of these mysterious fossils, commencing 
with the examination of the fossil, represented Plate XII. Fig. 6. 
This is a light yellow calcareous stone, on the surface of which arise, 
at nearly regular distances, though not apparently in any determined 
order, many small semi-globular, striated, and projecting bodies, 
which, by the aid of a lens of about an inch focus, are found to be 
formed of plates, regularly placed round the middle of these bodies; 
T 
VOL. II. 
