82 



It is remarkable for the bending of its filaments, and not 

 less so for the holes apparently formed by the Mytilus tu- 

 nicatus, (which I find abounds in variety of petrified Corals, 

 &c, found between Oxford and Bristol, — see tab. 323.) 

 There are also cases of Serpulce about it. This proves that 

 the structure of the substance preceded that of the Mytilus, 

 and that it may have been coeval with the Corals, or even 

 of earlier formation. It is sometimes dull and opaque, 

 sometimes almost transparent, and nearly as shining as 

 Satin Spar*. 



* I must here remind my readers, that the habitat I have given for Satin- 

 Spar, tab. 5, p. II, is correct ; for some other authors have, by mistake, and 

 by copying from each other, named Derbyshire for its habitat, and this 

 seems to have originated with Jameson, who probably purchased some speci- 

 mens there, and where, not long since, has been found striated Gypsum or 

 Sulphate of Lime, so compact as much to resemble the Satin-Spar, and like 

 it has been cut for ear-rings, necklaces, &c. The former may be readily dN 

 stinguished from the latter by being easily scratched by the fingeTr-naih 



