>Thanks Andrew,
>
>So this feature is actually the shell structure?   I think I was misleading
>by using the term 'nacre' (I apologize).

"Nacre" is often used for apertural and overglazing material. I
should say that I BELIEVE I am correct in saying that nacre is
actually pearly material, and has a distinct crystalline structure
which refracts light to produce the pearly appearance.

>What I meant is the actual
>surface "feel" of the shell... which you explained with the term "shagreen".
>
>
>So does Cypraea (Umbilia) armeniaca also have this shagreen sculpture?   If
>not, why?  :)

I haven't seen a specimen, but would think it may well do so. My own
U. hesitata are packed away and inaccessible, so I can't examine them
to check for this. If you have a 10x lens or a microscope you could
check for it. It ids of course possible that these shells do not have
shagreen sculpture...
--
Regards
Andrew