Lynn, Paul, and all Conch-L terrestriophiles,
 
From my observation and experience with land shells both in the field and
preparation for collections, almost all terrestrial and tree dwelling
mollusks have some sort of periostracum.  The only exception to this are
the calciphile species such as the limestone dwelling operculates, and
similar species.
 
Land shell periostracum can be a thin transparent, or translucent covering,
or an opaque and tinted covering that envelops the entire shell.  In the
case of many Helicostyla and related genera, the periostracum forms an
intricate pattern that, from the collector's point of view, adds an
aesthetic quality to the shell.  This patterned periostracum is sometimes
referred to as cuticle.  Unfortunately, as we know, bleach will remove all
types of periostracum.  And many land shells, especially the commercially
collected shells, are batch bleached loosing any hint of periostracum.
 
Many of the ground-dwelling terrestrial mollusks have a thin, or thick
chitinous-like periostracum that in some species tends to become flaky and
peel off over time.  I personally find the periostracum an important
component or characteristic of the shell.  In a few cases, it can also help
aid in the identification of the species.
 
The thin transparent, or translucent periostracum of many species does tend
to intensify the color of the shell underneath.  The Amphidromus species in
the subgenus Syndromus, and one species in particular, A. (S.) inconstans,
have a base shell color of bright yellow (see the cover of the March 1997
issue of American Conchologist).  With the periostracum intact, the yellow
color is deep yellow -- almost approaching a yellow/orange in fresh
specimens.  When the periostracum is bleached off, the yellow color becomes
extremely light, almost yellow/white.  The yellow pigment is in the shell,
but the periostracum adds a tint that deepens the color; almost like
holding an amber colored photographic filter to your eye and viewing a
yellow object.  This intensification of color is exhibited with most of the
Syndromus species.  In the case of A. inconstans, both the light and dark
tints are aesthetically pleasing, so it is personal choice whether you keep
the periostracum intact.
 
Removing the periostracum in some species can also cause another problem.
For instance, the large Megalobulimus of South America have a thin, but
tough ochre/amber colored periostracum which adds a sheen to the surface of
the shell.  When bleached, some of the Megalobulimus shells become dull and
chalky such as M. oblongus.  The periostracum-less shells of other
Megalobulimus such as M. terrestris are shiny, so it really makes no
difference whether you remove the periostracum, other than the tint of the
shell.
 
On the other hand, if you bleach a species like Asperitas everetti, the
large, dark green Ariophantid from Flores Island, you will be sorry.  What
you will be left with is a drab, mauve colored shell with virtually no
resemblance to the fresh shell with periostracum; similar to what happens
with Helicostyla florida previously mentioned by Paul -- green to white.
 
It would be next to impossible to list every land species to indicate
whether bleaching would be a benefit or detriment to the shell.  My
suggestion is not to bleach any land shell when at all possible.  In fact,
the small thin-shelled species may dissolve if dunked in bleach.
 
Use a soft toothbrush and mild soap to brush way exterior dirt and debris.
If the periostracum seems to obscure shell color underneath, then it is
personal choice whether you remove it or not.  As previously mentioned in
this thread, an option would be to display one with and one without
periostracum.  But that often is not an option.   The rule of thumb is, if
the shell has color, don't bother bleaching; if the shell is drab and looks
like it would benefit from cleaning, then use the toothbrush and mild soap
route.  Nine times out of ten you will be glad you did.
 
Rich
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Richard L. Goldberg
Worldwide Specimen Shells
P.O. Box 6088, Columbia, MD 21046-6088
phone/fax:  (410) 379-6583
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homepage:  http://www.erols.com/worldwide
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our one year anniversary on the Web
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At 07:50 PM 1/3/98 -0600, you wrote:
>Hi Paul,
>
>Isn't it true that the color bands in many land shells is composed of
>periostracum, and that periostracum being organic, will be eradicated by
>bleach? Is this true of all land shells or just certain groups, and if so,
>can someone tell us which ones are bleach-susceptible?  I seem to remember
>that all Liguus are colored by their periostracum.
>
>Also, Paul, you describe Helicostyla pan both before and after bleach.  Is
>it recommended that one show the species which have periostracum forming
>their color both with and without their colorful outer "skin"?
>
>Lynn Scheu busy digging out from under 10 days' email after a trip to
>Oregon, and recuperating from some horrendous Oregon brand of flu, doubtless
>blown in out there by El Nino. If any of you meet anyone with the wretched
>stuff...don't be polite, don't stop to trade shells... just run away!
>
>>Holiday Greetings All!
>>
>>I hope that you haven't all rushed off and turned your Helicostyla florida
>>specimens into albinos, based on my previous posting about land shells and
>>bleach.  I thought that H. florida was one of the species I had successfully
>>cleaned with bleach in the past, but after posting this information, I had a
>>nagging doubt, so I tried one just to be sure.  OOPS!  H. florida is NOT a
>>bleach-stable species - it comes out white as snow.
>>
>>While on the subject, Helicostyla pan is another interesting one - a very
>>interesting shell, both before and after bleaching - arguably more
attractive
>>after bleaching.  Before bleaching it has multiple spiral bands ranging from
>>deep chocolate brown through lighter brown, tan, and white.  After
bleaching,
>>the bands are gone.  The lower half of the body whorl is deep chocolate
brown,
>>which extends up along the suture line.  Upper half of the body whorl is
tan,
>>fading to white near the brown suture.  The shell has a nice gloss, which of
>>course is not visible when the periostracum is intact.
>>
>>Regards,
>>Paul M.
>>
>>
>
>