Dear Art,
let us consider Erosaria nebrites Melvill, 1888 and look at pictures 15-28
on Plate 81 of "A Guide to ...." by Lorenz & Hubert. We can see in figs. 26,
30 a shell having a dilated and callused outer lip;  this is f. dilatata.
This form is found in all known to me populations of E. nebrites never
comprising the majority.  Similar
shells (the same form) may be found also in populations of  E. erosa,
Erosaria lamarckii,
Erosaria turdus and so forth.
Shells having unusually dark colorations are found in many cowry
populations. All such shells may be called f. saturata  These are many
examples
of forms in molluscs, not only in cowries.
E. nebrites may be used as an example of subspecies. It was mentioned by
Melvill  as a variety (form) of Erosaria erosa. Dorsomarginal blotches,
which are present in shells of E. erosa, are absent in shells of E.
nebrites. Later malacologists discovered that a distinguishing character-the
absence of dorsomarginal blotched-is present in the vast majority
(practically in all) of
erosa-like shells of the Red Sea and recognized these populations as a
subspecies of erosa: Erosaria erosa nebrites. It is restricted to the Red
Sea and the Gulf of Aden and, perhaps, to near-by areas. Burgess(1985), who
did not recognize subspecies in principle,  mentioned finding specimens of
nebrites on American Samoa and concluded: "if it was nebrites and not simply
a freak erosa, then we must suspect that all nebrites are simply a variation
of erosa." That means that all nebrites inhabiting the Red Sea (billions !)
are simply freaks. Sometimes discussion between collectors recognizing
subspecies and these which do not recognize subspecies in principle
resembles debates between religious people and atheists: maximum,  agreement
can be reached to respect each other.
E. nebrites is recognized by many malacologists as a valid species. I think
this is correct. Almost correct, because there is a problem with the main
distinguishing (specific) character of this species -the dorsomarginal
blotches. They are absent in the vast majority of nebrites shells, but not
in ALL shells; these blotches are absent sometimes in shells of erosa too,
never comprizing the vast majority. This problem will be solved in the
future
These are examples of forms and subspecies. To collect and study them is, in
my opinion, is very interesting.
Ed

----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 17, 2003 4:53 AM
Subject: explanations


> Now that you have decided on what species is---or may be, I wonder if
there is a decent description of the difference between "sub-species" and
"form of-".
>   Enquiring minds want to know.
>    The Question Man
>
>
> PLEASE NOTE: My new, long-term, and correct email address is:
[log in to unmask] Please update your records!