Hi, everyone!

I need some help with several conchological
terms which appear to be used in different
ways in the literature.

What is a "fossula"?  I had thought it was a
vertical groove found on the inner lip of
cypraeids and ovulids.  However, Liltved, in
"Cowries and Their Relatives of Southern
Africa", p. 34, refers to the fossula as a
"columellar depression" and the ridge next to
it as the fossula.  Which is correct?

Also, the terms "columella" and "base" appear
to be used in different contexts in various
publications.  Some glossary definitions are
not clear.  What is the difference?

I look forward to your assistance.

Conchologically yours,
Ron Noseworthy