THE SHELL. 70 



tinctly be traced in the centre of the back. On 

 making an incision I found it superficially placed 

 within the substance of the mantle, whence it was 

 very readily extracted, having apparently no organic 

 adhesion to the flesh. A careful examination shews 

 a very close agreement with that of PL plumula, which 

 I have no doubt it is. Its length was exactly \ inch, 

 its breadth a little more than \ inch. It lay over the 

 dark brown liver : its own colour was darkish horn, 

 tinged with reddish : as it dried, a silvery nacre 

 covered it in parts, which gradually extended to the 

 whole. There were two radiating depressions on the 

 surface. 



