README File Names: FILE Matrix: Character state matrix for phylogenetic analyses and for morphospace analysis. The morphospace analysis employed the first 26 taxa, the genus-level phylogenetic analyses used the first 28 taxa (up to and including Mesodesma corneum), while all taxa were used in the species-level phylogenetic analysis. rows = species (total 46) columns = morphologic characters (total 88) outgroups used in phylogenetic analyses= Mya arenaria and Mesodesma corneum. Missing data symbolized by - if not applicable, and by ? if unknown. FILE Char_Descrips: Table of character descriptions for character state matrix. Left column = Character numbers. Correspond to numbers in character matrix. Middle column = Character and character state descriptions. Right column = Character states. Correspond to states in character matrix. Data collected by Laurie C. Anderson, Louisiana State University, glande@lsu.edu