Lynn,
 
At 01:22 PM 1/4/98 -0600, you wrote:
 
<condensed>
 
>Another landshell periostracum question, this one for Rich:
>
>Once I got a beautiful big landshell species from you, large ... maybe a
>couple of inches ... and brown and extremely glossy and impressive.  I laid
>it on a shelf where I was displaying some other landshell species (I may
>admire the critters, but don't pretend to know much about them, and am still
>somewhere in the curiosity stage of collecting them). It lived happily there
>for quite some time, and then one day I found it broken to bits.  Some
>pieces were on the floor and some were scattered about on the shelf....
 
This shell "was" undoubtedly a species of Paryphanta.  The Paryphantidae
are carnivorous land snails which range from South Africa, to New Guinea, a
few islands in the Southwest Pacific, Australia, and, of course, New
Zealand, where the genus Paryphanta is endemic.
 
In New Zealand there are seven genera in the Paryphantidae, but the largest
group are confined to the Powelliphanta, a subgenus of the  Paryphanta
(your specimen which exploded was from that group).  The reason the
Powelliphanta crack, and /or explode is due to the structure of the shell.
Its base is a very thin layer of calcium carbonate (paper thin or microns
thick) covered by a very thick chitinous outer layer (the periostracum).
Unless the shell is kept moist after the snail is extracted from the shell,
the periostracum dries up, shrinks and cracks the paper thin shell -- the
reason it explodes.
 
There are various methods for preserving the shell.  One is to coat it with
a non-coloring shellac or clear varnish, but one must be careful not to use
a glossy finish, as it starts to look unnatural.  The other is to soak it
in a glycerine and alcohol solution (75% / 25%) for 24 hours before
displaying the shell and repeat the process periodically to keep it moist.
Make sure the solution get way up into the aperture.  The problem with this
method is that the glycerine will ooze out of  the shell and gunk up your
shelf, box, or other receptacle for displaying the shell.  Let the shell
sit on a pad of paper towels for a few days after soaking to let the
glycerine drip off the shell.  Check the shell periodically to see that it
is moist.
 
There are probably other methods for preserving the Paryphanta.  The best
method will all depend on the climate you live in, and how you intend to
display them.
 
Rich
 
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Richard L. Goldberg
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