[Taxacom] Mollusca, major subdivisions (Lipocephala and Glossophora)

[Kenneth Kinman]

Dear All,
      I am not familiar with the work of Lankester, 1889, but he
apparently divided the molluscs into Lipocephala (for bivalves) and
Glossophora (for the other, radula-bearing, molluscs).  To me this seems
to be a very natural division of molluscs, into primitive forms (lacking
a head and a radula) and those taxa which possess these synapomorphies.                              
      Unfortunately, the vast majority of malacologists today seem to
believe that bivalves secondarily lost their head and radula.   My
question is this.  Did Lankester believe that the headless,
radula-lacking, bivalves were primitive or derived?                  
             ---------Ken Kinman