Phil,
Perhaps, I should have added the obvious requirement for a variation
analysis that the sample be unbiased with regards to any conchological
variable. The original collector may have intentionally or unintentionally
collected the larger or smaller specimens or may even have tried to collect
representative samples of both sizes in a non-random fashion. It is even
possible that the original lot may have been divided non-randomly &
distributed among other collectors. If you have no way of knowing the
circumstances, then you hope that it was a random sample.

The most practical way to collect an unbiased sample is to take either every
adult specimen in sight or, if that's not feasible, for example, there may
be too many specimens, to take a pre-determined number of shells, say, the
first 100 adult shells you find in an as small & as homogenous habitat as
possible.

Aydin

 -----Original Message-----
From:   Phil Liff-Grieff [mailto:[log in to unmask]]
Sent:   Tuesday, November 27, 2001 11:09 AM
To:     [log in to unmask]
Subject:        Re: Polygyra cereolus/septemvolva

Harry, Ayden and Kurt,

Thank you for your information.

I will check out the umbilicus of these specimens but, based on locality
alone, it looks like they are all cereolus.  As to the variation in
size, I hve about 100 specimens so it might be worthwhile to do an
analysis of the group.  Based on a quick visual survey, there seem to be
two very distinct size ranges.  Aydin, I will report back after I find
the time to sit down and measure them all.

Thanks again,


Phil Liff-Grieff
[log in to unmask]
La Crescenta, California

PS  Once again, Conch-L comes through with flying colors- even for us
land snail types!