Thanks Andrew,

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


Nancy Smith



§   -----Original Message-----
§   From: Andrew Grebneff [mailto:[log in to unmask]]
§   Sent: 16 January, 2004 0:44
§   To: [log in to unmask]
§   Subject: Re: Cypraea question: Umbilia nacre
§
§
§   >I have several specimens of C. hesitata, as well as h. beddomi and
§   >h. capricornica and wondered about the nacre of these shells...
§   >The pictures I've seen of C. armeniaca appear to have a 'typical'
§   >glossy nacre (typical of many Cypraea anyway) but the hesitata, h.
§   >beddomi and h. capricornica have what I would describe as a "matte"
§   >finish to their nacre.   Why are they different in this way, while
§   >all are members of Umbilia?   Or does C. armeniaca have a
§   matte-like
§   >finish as well?
§
§   Cypraea inductura ("callus"), I think you will find, is smooth down
§   to a microscopic level. That of Umbilia (one of the few good genera
§   in the family) probably have what is called shagreen
§   sculpture, which
§   consists of small anastomosing pustules etc; in some gastropods this
§   is large enough to be naked-eye-visible; in others it's microscopic.
§
§    From memory some volutids and olivids have visible
§   shagreen sculpture.
§
§   Strictly speaking nacre is so-called mother-of-pearl, as found in
§   triochids, pleurotomariids etc.
§   --
§   Andrew Grebneff
§   Dunedin, New Zealand
§   64 (3) 473-8863
§   <[log in to unmask]>
§   Fossil preparator
§   Seashell, Macintosh & VW/Toyota van nut
§   ________________________________
§   I want your sinistral gastropods!
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§   Opinions in this e-mail are my own, not those of my institution
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