The Echinoid Directory

Stem group clypeasteroids with:

• monobasal apical disc, with four gonopores;
• petals lanceolate, but never strongly conjugate, remaining open distally;
• test depressed towards peristome, no vertical walled entrance;
• periproct inframarginal to oral, flush;
• phyllodes hardly expanded adorally, only slightly developed, single pored. Ambulacra tapering adorally, pores in single iregular series with pyrinoid plating;
• bourrelets absent, basicoroanl plates short, no specialized zone of perioral tubercles and spines;
• buccal pores present at edge of peristome, not separated from other phyllode pores;
• no perignathic girdle supports internally.

Palaeocene to Eocene of Africa, Pakistan, and the French Pyrenees.