The Echinoid Directory

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

Key to the genera of Stomechinidae 1a. Multiple subequal tubercles on interambulacral plates throughout. Go to 2 1b. Single primary interambulacral tubercle per plate or just secondary granulation on plates above ambitus Go to 5 2a. Ambulacral pore-pairs in offset triads forming a broad adradial band. Go to 3 2b. Ambulacral pore-pairs in a single uniserial band at ambitus (may be biserial or uniserial orally). Go to 4 3a. Ambulacral pore-pairs in offset triads forming a single adradial band. Polycyphus 3b. Ambulacral pore-pairs in two discrete columns; pore-pairs of the inner series small. Thierychinus 4a. Interambulacra with an ambitual zone of low plates bearing much smaller tubercles compared to adapical and adoral plates. Pore-pairs biserial adapically. Diplechinus 4b. Plates above ambitus with reduced primary tubercles. Pore-pairs uniserial above ambitus. Baronechinus 5a. Pore-pairs arranged as a single irregular column at the ambitus. Go to 8 5b. A relatively wide band of offset pore-pairs extends from apex to peristome on each side of the ambulacrum. Go to 6 6a. Sharp change in tuberculation at ambitus (coarse tuberculation beneath, fine above). Go to 7 6b. Only a rather gradual change in tuberculation at ambitus. Stomechinus 7a. Test subglobular. Codechinus 7b. Test hemispherical. Tiarechinopsis 8a. Primary tubercles clearly differentiated on ambital interambulacral plates. Echinotiara 8b. Three subequal tubercles on ambital interambulacral plates. Microdiadema