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4a. Marked reduction in size of primary tubercles above the ambitus; epistromal ornament with strong vertical component linking tubercles dominates aboral plates.
4b. Primary tubercles not markedly smaller above ambitus; aboral plates not dominated by coarse epistromal ornament.
5a. Pore zones offset in triads.
5b. Pore zones uniserial or in weak arcs throughout.
6a. Epistroma in the form of zig-zag vertical ribs and grooves.
6b. Epistroma in the form of reticulate ribs and grooves surrounding primary tubercle.
7b. Ambulacral plates with primary tubercle and smaller secondary tubercle immediately above and perradial to it.
8a. Plates densely tuberculate. Ornament confined to pits around primary tubercles. Primary tubercles non-crenulate.
8b. Plates sparsely tuberculate aborally; ornament consisting of sparse radial bars around primary tubercles. Primary tubercles weakly crenulate.
9a. Plate ornament of reticulate epistroma highly developed.
9b. Plate ornament restricted to sparse radial bars around primary tubercles.