Cephalaspidea is an Order of the Gastropoda with most snails bearing an external shell. They are of special evolutionary interest because traditionally the group has been considered the most basal offshoot of the Opisthobranchia, but this phylogenetic position is nowadays disputed. Moreover the validity and definition of most families and genera is not well established and their relationships are poorly known. This results, somehow, from inadequate descriptions in some cases based on shells alone or few anatomical characters, which seem to be too variable for phylogenetic inference. This project aims to achieve a complete family and genus-level phylogeny of the Cephalaspidea inferred from molecular sequences of mitochondrial and nuclear genes. The goals are to investigate the monophyly of families and genera and their phylogenetic relationships and shed light on the overall systematics of the group.