The monophyly of the genus Echinocardium is based on two synapomorphies: an anal branch is added to the subanal fasciole, and the labrum is short and bordered by two pairs of ambulacral plates.
Synapomorphy: the length of the internal fasciole reaches 50% of the test length [ILLUSTRATION FOR FIGURES 1-3 OMITTED].
Synapomorphy: many more than ten pore pairs enclosed in the fasciole [ILLUSTRATION FOR FIGURE 1 OMITTED].
Spiral ridges thinner than axials in intervals, expanding on ribs to form angular nodules, ridges nearly equal in strength, adapical row slightly the stronger, abapical one slightly weaker; first two whorls with two rows of nodules plus a third usually beginning to develop above suture, later whorls with three main rows of nodules, plus a weak ridge immediately below suture; last whorl with a shallow waist-like furrow at base of rostrum containing a thin ridge, strengthening and bearing angular nodules on dorsum; rostrum forming a moderate fasciole, which bears 3 ridges weakening anteriorly, the upper 2 with angular nodules.
Axial ribs straight, slightly prosocline, moderately weak below suture, evanescing below "waist", fasciole with strong nodules; ribs in t/s more or less angularly rounded, with sloping sides, ribs wider than their intervals, 8 per whorl; bases of ribs narrowing where they cross basal "waist", where they are separated by foveolate interstices.
Axial ribs somewhat arcuate, slightly opisthocyrt on last whorl, reaching and crenulating suture, evanescing on upper part of rostrum, fasciole with strong nodules; ribs in t/s strongly rounded and slightly compressed on spire whorls, lower with sloping sides on last whorl, ribs slightly wider than their intervals, one behind lip high and varicoid, 12 or 13 axials per whorl.