« The Donacidae may be defined as those Tellinacea that are relatively trigonal, equivalve, and that lack either a posterior flexure or a gape. The ligament is entirely external but not seated on a conspicuous nymph. There are 2 cardinal teeth in each valve and well-developed lateral teeth in the left valve, with corresponding sockets and sometimes lateral teeth in the right valve. » – E. V. Coan: “The northwest american Donacidae”, The veliger vol.XVI, erkeley 1973, p.131.
 

Shell bivalve, equivalve, inequilateral, usually truncated posteriorly and lengthened anteriorly. Beaks opisthogyrate; ligament external; pallial sinus deep (G. Lindner: Muscheln und Schnecken der Weltmeere, München 1999). The sculpture is mainly radial, and mainly visible at the pallial margin.