different depths ; by which the peculiar spongeous structure, already 

 noticed as belonging to these bodies, was perceived ; but no appear- 

 ance of spines could be detected. 



The specimen was then immersed in dilute muriatic acid, and exa- 

 mined at different periods, to ascertain whether the new surfaces thus 

 obtained displayed any particular appearance. After rather more than 

 a quarter of an inch of its substance was thus removed, I was pleased 

 to find, with a lens of moderate power, several cruciform spines, 

 formed, as it were, by two fusiform bodies, not an eighth of an inch 

 in length, crossing each other at right angles, and terminating at each 

 end in a very sharp point. 



When these bodies were first discovered, the specimen was still wet 

 with the water, with which the acid had been removed. In this state 

 they possessed a considerable degree of transparency, which they 

 rapidly lost, as the water evaporated : so that when dry, .they were 

 completely opaque, and of a chalky whiteness. From their possessing 

 this hydrophanous quality, and from their having withstood the action 

 of the muriatic acid, there appears to be the greatest reason for sup- 

 posing, that these bodies, which were originally the spines of the ani- 

 mal, are now formed of an hydrophanous chalcedony, and imbedded 

 ki a matrix of carbonate of lime, which has pervaded or has supplied 

 the place of the soft spongeous part. At Plate VII. fig. 8, is a repre- 

 sentation of the appearance which these bodies present when mode- 

 rately magnified. This and the preceding fossil alcyonia, are from Swit- 

 zerland. 



Alcyonium jicus, Linn, accurately depicted in the Metallotheca of 

 Mercatus *, as Alcyomum quint urn antiquorum, and particularly de- 

 scribed by Marsilli as Figue de substance d'eponge Sf d'alcion-^, re- 

 sembles much, in form, the brown silicious fossil, Plate IX. Fig. 4. 



* Arm. 6. C. 6. p. 102. 



f Histoire Physique de la Mer, p., 87. 



