Mollusca is a phylogenetic concept, not a morphological/anatomical concept (Pojeta, 1980; Runnegar and Pojeta, in press). In order for a taxon to qualify for placement in the Mollusca, the taxon must be shown to be phylogenetically related to other taxa in the phylum. In point of fact, Mollusca cannot be defined morphologically/anatomically. The only acceptable definition of Mollusca is that the phylum is made up of its contained taxa.