The Echinoid Directory

 Scutellidea with:

• complex internal buttresses forming microcanal system around periphery;
• four gonopores;
• ambulacral and interambulacral zones similar in width at ambitus; pores and tube-feet extending onto interambulacral zones;
• petals well-developed, closed or nearly closed distally;
• basicoronal circlet small, interambulacral elements pointed but not strongly projecting;
• posterior interambulacral zone disjunct adorally;
• periproct opening oral, associated with first pair of post-basicoronal interambulacral plates;
• perradial notches or lunules in some or all ambulacra;
• food grooves well developed, bifurcating at edge of basicoronal circlet and finely subdivided distally.