The Echinoid Directory
Key to the genera of Scutellidae (1)
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1a.Interambulacral zones continuous on oral surface. |
1b.At least the posterior interambulacral zone disjunct on oral surface. |
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2a.Periproct midway between peristome and margin; opening within first post-basicoronal plates. |
2b.Periproct supramarginal to submarginal. |
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3a.Petals 50% or less of radial length. Test very thin. |
3b.Petals 60-70% radial length; test rather thick. Test not especially thin. |
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4a.Posterior ambulacra strongly indented. |
4b.Outline subcircular. |