David and others,

The late Stephen J. Gould and collaborators*** shared David's perception
and addressed the problem with a morphometric analysis of five anomalously
sinistral specimens of Cerion, a Bahamian landsnail which was a already an
established favorite of the senior scientist. Using Xray images of the
shells to enhance the number and quality of measurements, they showed the
sinistral shells differed from dextral mates in more than just the
direction of coiling - the lefties had smaller apertures and a unique twist
in the coiling axis.

In September of the next year Dr. Gould, lamentably not available for
further elaboration, wrote and asked me to collaborate on a project related
to just this problem.  Malacologist Robert Robertson had informed him of my
collection of mutant sinistral shells (mostly of marine snail species)
species, as exemplified at <http://www.jaxshells.org/reverse.htm>, and
"Steve," as he insisted on being called, wished to test his Cerion
hypothesis on my specimens.

About a month later, and incidental to a family vacation in NH, I toted
about fifty of my treasures to New England and gave Steve the suitcase-full
(not unlike an espionage exercise - and to the continuing amazement of my
three children and wife) at Logan Airport, Boston.

The protocol was based on a morphometric analysis of two dozen normal
specimens from the Museum of Comparative Zoology posed in juxtaposition
with the one reversed species-mate from my assortment on an Xray cassette
(I have a couple of these arrays on file). Regrettably, although the study
was progressing OK for a while, it never reached fruition.

I've thought a lot about this matter, and I've looked at a lot of shells in
mirrors.  On reflection (argh!), I think Steve was right for a substantial
portion of these anomalous shells.  There are also, however, a significant
number of instances which seem to involve perfect reversals.  Further, as
once pointed out by Richie Goldberg, there are two factors here: our
tendency to see the (even perfectly formed) sinistral as something less (or
more) than a mirror image - and the actual Gouldian phenomenon of
"multiple" anomalies in shell form in the reverse-coiled mutants.

Harry

*** Gould, S. J., N. D. Young, and B. Kasson, 1985. The consequences of
being different: sinistral coiling in Cerion. Evolution 39(6): 1364-1379.

PS: Can anyone explain why I'm not getting Marien Faber's postings?  I got
David's response (on this thread), which included the posting by Marien,
but no direct posting!


At 02:06 PM 12/2/2004, you wrote:
>Harry and all,
>
>Seeing these specimens side by side raises a question for me I've had for
>while. When I see a sinistral shell, I have a very strong sensation that the
>shell is tilted or skewed--a sensation I don't have with dextral shells.
>
>This comparison makes it really obvious: at least with some sinistral
>shells, they really aren't just mirror images of dextral ones.
>
>David Kirsh
>Durham, NC
> >
> > To listers who want to see the subject of this discussion,
> >
> > Click on <http://www.jaxshells.org/pyrum1t.htm>
> >
> > Harry

Harry G. Lee
Suite 500
1801 Barrs St.
Jacksonville, FL 32204
USA
Voice: 904-384-6419
Fax: 904-388-6750
<[log in to unmask]>
Visit the Jacksonville Shell Club Home Page at:
www.jaxshells.org

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