Order1:-Phanerozonia
1) Arms are provided with two rows of conspicuous marginal plates.
2) Oral plates are infra-marginal and aboral plates are supra-marginal.
3) Pedicellariae are alveolar or sessile type.
4) Pedia or tube feet are arranged in two rows.
5) Mouth frame is well developed and adambulacral type.
Order2:- Spinulosa
1) Arms are generally without conspicuous marginal types.
2) They have infra-marginal oral plates and supra- marginal aboral plates.
3) They have alveolar or sessile type of pedicellariae.
4) They have tube feet which are arranged in two rows.
5) They have well developed mouth frame and adambuacral type.
Order3:- Forcipulata
1) They have marginal plates which are inconspicuous or absent.
2) They have aboral skeleton which is mostly reticulate with conspicuous spines.
3) They have tube feet which are arranged in four rows and provided with suckers.
4) They have Papulae on both surface.
5) They have mouth frame of ambulacral type.
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