Some capulids and hipponicids are suspected of parasitism; the parietal
area may be an easy spot from which to reach the host.

In part, the preferential collection of nice-looking shells may be a
factor.  Sabia does occur on other parts of the shell, but may either form
an obvious flaw or, by making the shell appear plain and lumpy, camoflage
it somewhat.  I think Gary's Encyclopedia of Seashells illustrates Sabia on
the spire of a cerithid, although I do not have it handy to check.  The
Southern Synthesis illustrates one on the spire of Conus.

The Southern Synthesis cites two species of Sabia, S. conica and S.
australis, as well as other genera.  It says that Sabia tends to occur with
hermit crabs, so the parietal area would be a relatively sheltered spot as
the shell is dragged.

Dr. David Campbell

"Old Seashells"

Department of Geological Sciences
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315
USA

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919-962-0685
FAX 919-966-4519

"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug