Ill 



The edge of the upper part, or that which forms the base of the cone, 

 is either pierced with several holes, or else is marked with traces of 

 holes, which are now filled up with flint. The lower termination, 

 which forms the apex of the cone, is also either pierced with one, and 

 sometimes with two holes, or bears marks which shew that such open- 

 ings have existed, but have been since filled up by silicious matter. 

 The specimen, Fig. 15, will give a tolerably correct idea of the gene- 

 ral appearance of these fossils. 



Anxious to obtain what knowledge I was able respecting the forma- 

 tion of these pebbles, I broke many of them in different directions, 

 and was thereby enabled to ascertain, that their shape and their open- 

 ings depended on the figure of a body, which they contained in a ca- 

 vity in their central part. This was, of course, seen with more dis- 

 tinctness in those which, as in Fig. 16, had been broken in a perpen- 

 dicular direction. 



By the aid of the opening made by fracture, Fig. 16, some of the 

 remains of this body will be seen. It will be there perceived, that it 

 is formed by a congeries of tuberculated tortuous filaments, which, by 

 intertwining with each other, form, in the apex of the cone, which I 

 presume to have been the inferior part of this body, a closely reticu- 

 lated columniform body, which, after having proceeded less than an. 

 inch, appears to have separated into about a dozen ramifications 

 formed in a similar manner. At the superior part, on the side, a por- 

 tion is still adherent, in which the original characteristic forms of the 

 ramifications of this body may still be seen, bearing a slight resem- 

 blance to the formation of the fan sponge. 



That this body has derived its origin from some lost species of alcy- 

 onium or of sponge,! am firmly of opinion ; and trust that in this opi- 

 nion I shall be joined by those who are acquainted with the charac- 

 ters of these two genera. Positive evidence will not be obtained 

 until the nature and form of this body is ascertained in some more 

 perfect specimens : the difficulty of procuring which is considerable, 



