We strike again.
      This is certain to sound obvious. But I have not seen it
discussed. It seems that smooth, streamlined shells (Olives, Cowries,
etc.) are more apt to spend a good part of their lives submerged
under a layer of mud or sand than are shells with stickers on them (M.
 pecten, Lambis, etc.) Smoothies can submerge easier. Stickers allow
for more protection out in the open.
    So the question is: are there exceptions to this phenomenon?
       Art