The US National Park Service has added a considerable amount of
information on unionids to their web site.  A few figures are in the process
of being added, but the text is complete. You may want to link this to your
own web site as it is particularly suited to students, teachers etc.  The
site is:
     http://www.nature.nps.gov/wrd/mussels/TOC.htm
Marian E Havlik
Malacological Consultants
1603 Mississippi Street
La Crosse, Wisconsin 54601-4969 USA
Email: [log in to unmask]
Phone/Fax: 608.782.7958