Recently, studying my photos of Tritonoturris, I read carefully the
descriptions of the 4 species included in E. Alison Kay's Hawaiian
Marine shells.  Some question arises about the difference between a
varix and a rib.  Normally, ribs are reasonably uniform in size and
spacing.  Varices are of two kinds:  a terminal varix that occurs only
when the shell becomes fully mature and repeated varices which may be
regularly spaced, or irregularly spaced but are larger than ribs on the
same specimen.  That seems clear, but when the only axial sculpture is
so small as to be considered an axial thread, and varices are described
as uniformly spaced, it is not clear whether the varices are actually
ribs.

What is the dividing line between ribs and varices?  It would seem that
axial ribs are varices of a regular spacing and size and occur during
resting stages in shell growth when the shell is thickened.  In
intermediate stages of growth the lip is thin, and often internal lip
sculpture is lacking.  The apparant purpose of ribs is structural
strength.  Any comments on ribs vs varices?
--
                     Aloha from Wesley M. Thorsson
Editor of Internet Hawaiian Shell News, a monthly Internet Publication
           122 Waialeale St, Honolulu, HI  96825-2020,  U.S.A
       http://www.hits.net/~hsn                 [log in to unmask]