Urechinid holasteroids with:
- thin test;
- orthosternous plastron (labral plate followed by single symmetrical sternal plate then a pair of episternal plates). Labrum usually separated from sternal plate by ambulacral plates;
- no rostral plate;
- apical disc 'compact' with single anterior genital plate followed by ocular plates II and IV both of which house gonopores. Posterior oculars disjunct from remainder of disc.