John brings up a very good point -- "...
variation within populations." -- all too often,
and especially with Amphidromus shells collected
for the collector market from one population are
sorted out by general color form and
unfortunately become distinguished as different,
even though all of these color forms are totally
mixed in their habitat.  I know of at least one
instance where an Amphidromus has been named
based strictly on color form, yet the particular
named color form is found on the same trees as
three or four other color forms.  That is not to
say that there are not distinct and isolated
populations exhibiting unique
characteristics.  There are numerous
examples.  Knowing the source and ecology of the
shells helps to determine whether a color form
(and I say this loosely) deserves consideration
for taxonomic separation.  Then the onus falls
upon the researcher to determine if the shell has
already been described in the literature.
Rich
~~~~~~~~~~~~~~~~~~~~~~~~~~~
www.worldwideconchology.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~

At 06:07 PM 5/7/2007, you wrote:
>Thank you Patrice.  Your discussion is
>zoologically sound and as Paul C. says the jelly
>makes it tougher but this is what the code tries
>to capture.  My only caveat is that most shell
>collectors concept of a form is not related to
>geography but rather variation within
>populations.  I.e., the albino form, or the elisae form in Regiconus pennaceus.
>
>John
>-----Original message-----
>From: BAIL PATRICE [log in to unmask]
>Date: Mon, 07 May 2007 05:59:41 -0500
>To: [log in to unmask]
>Subject: forma and variation
>
>Dear Conchlers,
>
>The concept of "form" must be clarified. It is often confused with
>individual variation:
>
>Valid species: any population, genetically isolated, without
>noticeable intergrades with other neighboring or sympatric
>populations. This concept is more biological than morphological and
>hard to prove so that in most cases, the stability of phenotypes is
>the only source data for determination.
>
>Subspecies: an aggregate of phenotypically similar populations of a
>species inhabiting a geographic subdivision of the range of that
>species and differing taxonomically from other populations of that
>species (Mayr, 1991). Intergrades between subspecies occasionally
>appear.
>
>Form: designates specimens with one or more dominant character(s)
>closely connected to a geographical area. Often used to indicate
>clinal variation.
>
>Varietal names: designates « individual » variation in shape or color.
>
>Form and varietal names have no taxonomic status, but these neutral
>terms are very convenient to distinguish phena in many faily of
>mollusk. "Forma" here corresponds perfectly to the definition given
>by Mayr (1991) for "The Race", a term not mentioned in the Code. The
>term variety which is, according to the Code deemed to denote
>infrasubspecific rank (after 1960), and which was rejected by Mayr
>(1991) is still often used in the malacological literature.
>
>
>Patrice Bail
>2 square La Fontaine 75016 Paris
>Tel:+33(1)45253330
>Fax:+33(1)40501390
>
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