On Ross Mayhew's website is a Turrid I scanned at 1200 dpi, processed in
Photoshop, then reduced to 72 dpi for online viewing. It's a bigger
shell (15 mm) than you are talking about, but it may give you an idea of
the resolution possible.
http://www.geocities.com/conchlimages/Monfils.html
Paul M.