The Echinoid Directory

Key to nucleolitid-grade genera

1a. Phyllodes extensive; pore-pairs aranged in oblique rows of three so as to form a single wide marginal band.


1a. Phyllodes short; pore-pairs aranged in two series approaching the peristome.

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2a. Test depressed, with concave anterior margin; anal sulcus trigonal.


2a. Test subconical to ovate, with convex anterior margin; anal sulcus rounded at apex.

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2a. Test ovate in profile with near vertical truncate posterior face.


2a. Test subconical in profile, without truncate posterior face.