A stereom arrangement which results in well developed pore-alignment running in one direction only.
A spine whose shaft is bent or angled at its end
One of the plates of the apical disc that lies interradially at the top of an interambulacrum and is pierced by a gonopore.
See buccal sacs.
A knob-like projection on the plate surface composed of glassy stereom. These never bear spines and are sutured to the test surface, not articulated.
A pedicellaria that bears large poison glands. The distal tip of globiferous pedicellarial valves end either in one or more fang-like spikes, or in a ovate pore ringed by teeth.
The small perforation through a genital plate that marks the external opening to the gonads.
See miliary granule: a microscopic mound to which pedicellariae and fine spinlets attach.