Hi Ronald, Andrew, Art, and all,

This is a great question and answer session. Thought I'd share
definitions as provided in "A Glossary of a Thousand-and-one Terms used
in Conchololgy", compiled by Winifred H. Arnold, The Veliger, Vol 7
Supplement, March 15, 1965. It's been a handy reference over the years.

abapical (L ab = away, apex = apex): away from the apex along the axis
or slightly oblique toward the base.

base (Gr basis = a pedestal): the extremity opposite of the apex of the
spire; basal: the bottom or lower part; basal lip: aperture margin from
the foot of the columella to the suture, part of the outer lip;
abapical.

columella (L columen = column):the axial pillar, the central pillar of a
univalve shell around which the whorls are built, extending from the
apex to the base; a portion of the columella is seen at the aperture of
most spiral univalves. columellar: pertaining to the columella.
columeller fold: spiral ridge on the columella projecting into the
interior of the shell. columellar lip: the inner edge of the aperture
including that part of it which covers the last whorl.

fossa (L fossa = a ditch, a trench): a shallow depression or cavity as
in Cuspidaria; fossette: a dimple, pit-like or small depression, a
depression for the resilium; the fossettes are placed at the hinge in
some bivalves; fossula: a little fossa or small pit with reduced
partitions.

inductura (L inductura = a coating, a covering): a smooth shelly layer
secreted by the mantle spreading from the interior side of the aperture
and over the columellar lip and sometimes over the shell exterior;
callus.


Cheers,

Bob Abela
Tamuning, Guam
http://www.guamcell.net/~babela/bobsguamshells/