137 



dered them as alcyonia, he was by no means convinced, that the} r 

 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 entirety 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 ; 



VOL. II. T 



