1) They exist in two forms namely extinct form and living form.
2) The living members are without stalk and free moving but the extinct forms are attached by stalk.
3) They have body which consist of an aboral cup , the calyx and oral cover or roof, the tegmen and are pentamerous in structure.
4) They have oral surface directed to upwards.
5) They have mouth usually at centre, anus away from centre present on the oral surface.
6) They have simple, mostly branched movable arms, usually five or ten in numbers with or without pinnules.
7) They have opened ambulacral grooves which are extended along arms and pinnules to their tips.
8) They have madreporite, spine and pedicellariae present on them.
9) They are commonly called sea lily.
10) They have sex organs in two reproductive bodies.
From what I learned before, crinoids do not have madreporite, spine and pedicellariea
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