The Echinoid Directory

• Home
• Introduction
• Morphology
• Keys
• Classification
• 3D models
• Index to taxa
• Glossary
• Log in

Key to genera of primitive irregular echinoids 1a. Single large primary tubercles present on intermbulacral plates. Mesodiadema 1b. Distinct primary tubercles absent. Go to 2 2a. Periproct enclosed by apical disc. Go to 3 2b. Periproct separated from apical disc. Go to 4 3a. Anal sulcus present. Menopygus 3b. No anal sulcus. Jesionekechinus 4a. Periproct inframarginal. Infraclypeus 4b. Periproct marginal to supra-ambital Go to 6 6a. Apical disc elongate with small auxilliary plates incorporated between paired oculars and posterior genital plates. Desorella 6b. Apical central, tetrabasal with 4 gonopores. Genital plate 2 separates posterior genital plates. Two small auxilliary plates incorporated between posterior oculars. Galeroclypeus